I am frustrated and would like advice on how to best handle these situations in the future...

I am responsible, take initiative, I tend plan ahead, I'm proactive, etc.
My DH is the opposite. He procrastinates, isn't necessarily proactive, and rarely takes initiatve. He has three kids, I have one, and then we have one together.

So, after we got married, I began to take on a lot more than I should have and immediatly had to start setting some boundaries on what I was willing to take on and how much responsibility was going to fall on my shoulders. Needless to say, we have had some struggles and many arguments over the last three years while we have been blending our family.

Today I am frustrated, because yet again he had information that he knew about and chose to wait until the last minute to "figure out" what he was going to do, which of course means that I am the one who has to "fix it". And when I tell him how the situation could have been avoided and how it's inconvient to me to have to "fix it" he somehow flips it around and makes me feel like the bad guy and he feels "guilt tripped" so he will just take care of it himself because its his kids and his problem....(I didnt say that, he did).

An earlier example of what I am talking about is one time his ex told him that he would have to pick up his kids from school on a day that she was unable to. He forgot. He called me after they were already supposed to be picked up, and I had to quickly leave work early to get them because he couldnt leave work.

Recently, his ex told him about another day that she wouldnt be able to get his kids from school becuase she will be out of town (gave him approx two months notice) and he waited until the week of to attempt to get off work early...his co-workers already have other plans so he has to stay at work. He requests that I work overtime to be able to get off early to get them or suggests that my mom take them since he can't.

Had he told his co-workers earlier, he would have had a better chance of them not scheduling something the same day he needed to get off early, and now he's mad at me for "guilt tripping" him when I simply explained to him how this issue could have been avoided if he had not procrastinated. I have picked up pieces for him many times in the past for this exact reason.

I struggle with this because I know that we are a team and that we should work together and help each other out if one or the other needs it. I want our marriage to be one of companionship, mutual respect, love, cooperation, team work, etc. Im just really tired of being made out to be the bad guy when I am trying to set boundaries on what I should sacrafice to help him when this would have been a non-issue if he would have just been more responsible.

How can I set these boundaries without making him feel "guilt tripped" all while holding him accountable for the things that are his responsibility and yet still be a help mate.