C.,
There are only a few ways I know to spice up with kids around. Now if you have babysitters, there are thousands. One thing that works for me is to let hubby go to bed, you take a bath or a shower make up on hair done (it might take a while, but it's worth it) set some candles up, and wake him up! This way he's surprised and at this point he is relaxed because he's been asleep for atleast an hour. Another that works is to flirt all day. I know it sounds simple and corny, but if you say something sexy in his ear while he's watching the game (you know he's not getting off the couch) then he thinks about it. Wash the dishes with a white shirt on accidently spill and walk right in front of him (of course the kids are up so he can't do anything about it, but he will think about it. Whatever you can think of.. Hell, go to the store for milk, and call him... say what your thinking about. By the time the kids go to bed he will be all over you. It's nature. Have fun with it. It might not work. If he is stressed, get some warm oil or lotion and rub his back. If he feels better the results are better. Of course he may just return the favor one day...
When he leaves to go out of town there are also things you can do, like put a nightie he's never seen in his briefcase so he'll think of what you'll look like wearing it. Write a love letter, or collect some quotes and put in a ziplock bag for him to find, and then there is of course phone sex. Why not? Find something or things that you are comfortable with that show him you love him and want him even when he isn't there.
As far as his stress level goes, look at it from his point.. he has a family to take care of, it doesn't matter if you work or not he will always feel it is his job because he is man. He hates his job, goes in everyday to support you and your family. I don't know anything about your finances, but my husband will get frustrated and say something smart about taking care of my son (previous relationship) and I'll say well you didn't have to marry us! End of story. Maybe your husband is feeling resentful of your older children. Do you get child support? This is something the two of you need time to talk about, so even though you are wanting to spice up your sex life, work on your relationship as well. Taking care of one problem generally will fix some of the rest.
If you argue all the time it makes it hard to want sex because you feel like you are giving in even though you aren't. Keep everything seperate. Three rules my husband and I live by 1. Never withhold sex or money 2. Never say goodbye without saying I love you and 3. When arguing say what you need to say and walk away until calm.
And something else we learned is that when worried about money do the bills together so that you both know what is going out and coming in and can work on it together.
I know having a date night seems like a good idea to most people, but sometimes there isn't a babysitter or the money to do it. You can however spend the morning together before getting the kids up or stay up late one night after the kids go to bed and just sit on the couch watching a movie or play cards or have sex. It's hard sometimes, but compromise is always better than nothing at all.
Best of Luck!
J.