Arabella2, I think you have identified your trouble spots yourself. Everyone is right, your kids need more sleep. I feel for children this young anywhere between 6 and 7pm to be ASLEEP is fine. For their physical and mental development this much sleep is necessary, let alone giving you happier less grumpy children!
I also passionately believe that by sleeping with them in this communal arrangement, you are not doing them any favours. This is because children need to learn from us about relationships, in order to be able to form adult relationships themselves later on. They need to see that mum and dad want time together, to talk about adult things and do adult things! They need to see that you love eachother so much that you want time together as a couple. This makes them feel safe and secure, and funnily enough I believe it is healthy that children know that you have a life outside them - I think otherwise kids can feel a sense of responsibility for your happiness.
They need to learn to fall asleep on their own! In their own room! If you don't teach them to do this you are depriving them of a vital life skill.
One major thing that I hope doesn't offend you too much, but I must say - your husband has to grow up. BOTH of you should do bedtime. Or if he's been out at work all day, HE should do their bedtime alone as a way of spending time with them. At the very least you need a routine in which both of you take a full part. Again, this gives the kids security and takes away any confusion they might feel.
You are having a third baby - I feel you and your husband really must must get a 'child centred' routine going in order for all of your lives to have a chance of being happy.
Just remember, children NEED lots of sleep, they NEED a routine, and they NEED to feel the safety of knowing their parents are in charge. As they grow older the NEED independence from their parents. They don't need to sleep with you - they might LIKE it but they don't NEED it. So feel strong when it comes to their own beds!
I do hope you manage to get things sorted, but you can't do it on your own, you need your husband to become involved. He sounds like another child at the moment. I seriously would try to have some evenings out if you can get a babysitter, where you can start to discuss how things need to change. Being a man, I think you'll have to couch it with plenty of praise, tell him what he does well, what the kids love about him, etc, but be strong and get a plan for how things must change.
ALL the dads I know, if physically present in the home in the evening, take EQUAL part in cooking dinner, bathing, putting kids to bed. This is not unusual nowadays!!!!!!! Good luck and I really really hope you can get there.