I'm going to play Devil's Advocate, since everyone is sh!tting on you guys for moving. If DH is making good money where he is and sending his CS, it may be for the best. I'm of the view that if the situation between the houses is toxic, with a lot of PAS and poor boundaries, frequent back-and-forth might actually be worse for the kids. Does your DH have a long-distance visitation CO? If so, he should take his CO'd time and make the most of it, taking off work to spend time with the kids doing fun things and actually parenting. If transitions were chaos and stress for all involved, fewer transitions might be better. But i hope your DH makes the most of the time he DOES get. Fretting in between visits won't help. 

IMHO, coddled kids are far less capable of adapting and when that coddled kid is under the truly mistaken thought that they get a say or can be disrespectful, they need a knot jerked in their tail.

While my mom and dad sat me down to inform me of the situation and ask my opinion, there was never any misunderstanding that I was included in the decision. I was informed and my opinion was saught.  It was not my call.

Even in divorce/broken family situations, kids have to be clear on their place and held to standards of behavior, standards of performance and required to behave respecfully regarless of their fee fees.

Parents are duty bound for the their minor children to be the parent's responsibility. Beyond that, all else is purely up to the parent.  Kid fee fees are a distraction.  As for an ill behaved hurtful spawn,  that has to be countered with such a high level of abject misery that the kid will wilt into snivling tremors at the very thought of pulling that crap ever again. If I was the OP's SO, I would mandate the next visitation putting that kid on the longest nastiest bus route possible paying whatever unaccompanied minor feesl necessary, then that kid would get feletted when they arrived with reminders nearly constantly of how their dispespectful crap will not be tolerated.

Kids get mad at parents. We all have.  However, there are boundaries of respectful standards that cannot be violated without extreme consequences that will have that kid rueing the day they made that mistake.

Though no doubt there are instances where a parent moves for selfish reasons, that choice is entirely the adult parent's choice and the kids adapt to that and behave acceptably.

IMHO.

ETA and here's the kicker - SO finally did get custody of one of the SDs in her teens. She said BM abused her so he drove to her state and picked her up. Filed an ex parte and won due to her testimony. But after 3 years here SD's behavior and mental health were even worse. SO did not know how to parent her either. Just "being together" isn't enough. 

financially.

Rather than fold, she took out supplemental school loans and got a lawyer.  That started the never ending delay and reschedule cycle from the SpermClan... after DW would fly back to SpermLand for a court date.  Their goal was to bankrupt her and force her to surrender custody of SS.  ..... Then I entered the picture. That permanently put the financial big stick in our hands and we have used it effectively ever since.

Though it did not take long for DW to take the financial dominance position in her own right.  Spermidiot though he did get a plumber's license, always remained underemployed in the mistaken understanding that his CS would remain lower. Nope, the Income Shares model nails the NCP for increasingly higher CW even when the CP is dominatingly the higher earner. and the NCP's income stays flat or even if it goes down.  DW completed a dual major BS with honors, an MBA with honors and has had a successful career as a CPA.   Alone she earns far more than the entire SpermClan earns combined.

Once SpermGrandHag no longer carried the big money stick, she and they went into poor abused NCP clan pity and tears mode.

The pinacle of our delivery of financial dominance was when DW counter motioned a SpermGrandHag motion for my income to be added to DW's for CS calculation that the SpermGrandParent's income should be added to the Spermidiot's for CS calculation purposes because he lived in their rental property rent free,  they paid his CS on SS and the three younger also out of wedlock Spermidiot spawned half sibs by two other baby mamas, and... the SGPs raised the youngest three in their home with no help from their idiot serial statutory rapist son or the two other baby mamas who they paid CS to in order to keep those baby mamas from actually taking the three youngest.  We provided documentation on all of those facts.

When the Judge agreed to consider that motion SpermGrandHag and SpermGrandPa lost their shit.  "Why does it matter who pays the CS, or where (SpermIdiot lives), etc.... "  DW asked how much Spermidiot paid in rent, neither he nor SpermGrandHag could provide a number which locked the Judge into the fact that Spermidiot paid not a penny in rent and was in large part what motivated her Honor to consider DW's motion to attach the SpermGP's income for calculation of CS.

SpermGrandMa always tried to get my income considered, which is clearly excluded in SpermLand CS regulations. So when they motioned for my money to be considered, DW counter motioned that the SpermGP's income be added to the Spermidiot's.

Game on dumb asses!!!

The Judge ultimately declined to add the SGP's income to the Spermidiots, and did uphold the income reduction credit awarded to the Spermidiot due to "Stepdad's high income" but .... CS still went up by 600% that time so the SpermClan still got their asses handed to them... as usual.

Since BM's mommy and daddy are paying her way, motion to have their income included in hers for CS calculation purposes.  I would. Also, if she is not an earner at all, motion for an imputed income to be assigned to her. If ordered, both could reduce CS.  Even if the Judge does not order it, BM and her parents will stroke out when DH makes that motion.

Learn the CO inside out, upside down, and backwards.  Learn the supplemental jurisdictional rules for Custody/Visitation/Support, and learn the State Regulations. Use them to keep BM pummelled into submission.  It is harder to do for an NCP, but.... it can give the NCP enough ability to induce pain on the CP that the CP might crawl under their rock and stay there. Getting their crap made public record and then rolling those facts out to the Skids and to the community can be a huge advantage.  Even if just kept hanging over their heads.  Keep a clearly marked folder that sais "Cour Order/Private Investigator Report (BM's NAME)" and bring it to Parent Teacher Conferences, Mediation meetings, Skid Hand Offs, etc....   BM will likely start losing hair, start looking decades older nearly instantly, and when the kids start to learn the facts and start calling BM out on her lies and manipulations as DH seasons them with select readings from the CO, Regulations, Supplemental Rules, and keeps them abreast of the facts in an age appropriate manner, it changes the playing field.  BM lies, DH counters with the facts.

Lather... rinse.... repeat.

It certainly worked for us in keeping the SpermClan's toxic crap mostly mitigated. Even though they lived in the SpermLand jurisdiction where the CO was ordered and DW never returned after leaving for University out of State with SS (then 14mos old) in tow.  As SS asked us about SpermClan lies, we gave him the facts. As he grew up he started doing his own research in our Custody/Visitation/Support file cabinets.  He stopped letting them manipulate him and started calling them on their crap in real time when he was in SpermLand for visitation.  They hated that.  The kids need the facts and the truth in order to be able to protect themselves form the shallow and polluted end of their gene pool. While they growing up, and just as importantly when they are adults. Toxic manipulators in the blended family opposition don't stop their crap when the kid ages out from under the CO. They just direct all of their crap on the Skid(s).

Go for blood. And have fun doing it.