Depends on the BM.  My BM is sane.  Even if she didn't like something, she wouldn't go bat shit crazy over it.  So she might not be thrilled that I'm volunteering in the classroom, but her unhappiness would not spill over and make our lives miserable.  I'd have to rethink it if she was nuts.

Do it.  Who gives a shit what the BM wants?  She has zero say in what you choose to do in your home, in your family, or regarding your volunteer interests.

If you enjoy it then do it.

What the Skid wants really isn't a factor either. Though it is positive that he has asked you to do it again.

What business is it of BM's what you do with your spare time or where you volunteer?

BM probably hates that you even exist, are you going to stop existing?

If you liked it and want to do it, do it.

but not nearly as much as if I was the Bm.  I'm sure Bm didn't like it but she NEVER did it and the school needed voluteers.

I almost always felt kind of uncomfortable however, since I wasn't the Bm. 

I think Ss liked it but wished his mom would do it.  

We were almost always the ones to do school activities.  Bm could never keep track.  If he was supposed to bring something, it was always up to us to try and pick up the slack.  Even if Ss was at Bm's for something like, wear pj's to school.  Ss would call us to bring him some pj's because he didn't have any a Bm's or Bm forgot.

Luckily, Ss started staying with us for most of the school days when he started 2nd grade.  Previously, Bm had him enrolled in school 30 min. away from us. 

However, for a few years, Bm did get Ss on one school night.  That went south when his grades started slipping due to homework not getting done on her night and her saying she just can't help him with it.

So, bottom line, like someone else said, if you and Ss enjoyed it and the Bm isn't going to go off the deep end.  Do it.

Enjoy that you young (assuming) step child wants you to participate.  Thats a decent sign he is not subject to pathogenic parenting by bm.

Have fun with him. In the mean time do NOT over look, ignore,  your bio kids for 1second if you have any.

BM's opinion means NOTHING.

So have fun! I volunteer for the skids, and it's great! Even met another SM doing the same thing while I was doing it!

Yes. I base my decisions more on what my skid wants than how BM feels. I volunteered heavily for Kinder. I was there about once a week either for lunch or just helping his class with crafts and parties and such. BM found out the next year and started going to lunch with him weekly. He told me he prefers it when she goes because she brings him fastfood (against school policy) so I told him that it was fine with me and now I dont go to lunch with him at all. Now I do still go to the parties and field trips but usually I’m just there as a photographer. I snap pictures and keep DH company when SS runs off with his friends. BM and Fiance3 also come so it’s 4 parents to one child. It’s a bit much so I distance myself from them and just help out the teachers with other stuff. 

There will be lots of volunteers in his classroom who aren't his mommy. What the heck makes BM think she gets to police that? No one should be stopped from helping in a classroom that isnt a danger to the kids. Tell BM to go whine to the teacher that OMG A STEPMOM INSTEAD OF AN ACTUAL MOM volunteered in their classroom and see what they have to say.

Teachers, in general, are thrilled with whatever adult assistance they can get.

It can also be a bonding thing for you and your SS.

Do it. Forget what BM wants. If she doesn't want you near the school, she better put a restraining order on you so you can't go near the kid, but without justifiable cause, she can't and the judge will just laugh at her. "She's bearing and abusing my child and neglects him everyday" is a good cause but if it's not true, she'll look like an idiot for false accusing. "I don't like her doing things to bond and strengthen her relationship with my child" is a good cause to get her punched in the face by many people after the judge is done tearing her a new one. 
 

what I'm trying to say is, she can't do crap if you want to volunteer so if you enjoy it and if it makes you and your Skid happy, freaking do it. I do everything with my Skids while BM does nothing and has no involvement whatsoever. 
 

if it makes you happy, that's good. If it makes your Skid happy, even better. If your DH is glad you're bonding with your Skid, that's great! If it pisses of a toxic HCBM.... HUGE BONUS! As long as you have the Skid's best interest in heart, you can't really go wrong.