My absolute favorite gifts that I get from DH are when he takes care of annoying things for me. One year I just asked for him to wash my car, because I never get around to it. This year I asked him to get my knife that I use all the time sharpened, and I asked DD to make me a loaf of challah (I will never do it for myself, and she makes a delicious one — I asked her to throw chocolate chips in, yum!). Are there specific things that your wife does that she doesn't enjoy that you can do for her? Or things she enjoys but never has time to do for herself? Although with four kids in a trailer, maybe you can just give her coupons for X days off of the kids to do what she wants!
Come to think if it, my favorite gift ever from DS was a coupon jar, filled with coupons for everything from a hug to doing the dishes one night.