I've got number 3 arriving soon, and so DD2 decided to go from being perfect sleeper to needing me there all the time whilst falling asleep (and also afew weeks of INSANE tantrums at bedtime). DD1 is therefore getting to bed late. SO... I had to make a few changes. Firstly I did have to put them both in the same room (in a bunk) but DD1 only goes in once DD2 is asleep(unless it's after 8.30pm). DH was not being helpful so I decided we needed to talk! I said I was going to implement some rules that could not be broken and he'd have to follow. So this is what we've done:

1) Give her a choice, clean teeth first or nappy on first.
2) the two book rule. Pick two books and that is IT. DH was letting her have 5. This took a few nights but she got used to it. That is the thing, when setting the rules they will get used to it.
3) being organised, having DD1 ready for bed and homework done, and then she can watch some TV.
4) DH was doing nothing, so as of last week, he is now on teeth/nappy/story duty and I go in for sleep. I can't tell you how much this has destressed me. I was losing it too, and shouting and going insane, crying you name it, because DD2 was playing me. So now DH has to be responsible (which he'll need to be when Im in hospital) and it also shows him what I have to do. I find so far it's worked well. I think DD2 liked the reaction she got from me. She now knows there are firm rules, and I think it's helped DH realise we need rules.
Maybe if you could get your DH to do the bedtime routine? That way you're with the older one (like I am now) and we can have time together.
Good luck xoxo