OP, talk this over with your husband. As a PP said, he has to be involved in the planning and the actual hosting by taking a day or two off. Like another PP said, your hosting can actually be hosting-lite, since they're close family and they're coming for a whole week. Let them do some of the meal planning, shopping, and cooking. Let them spend days by themselves doing touristy things; no doubt that's their preference anyway, instead of having you along on all excursions. Since you work part-time, you can just keep your schedule value and leave the house on an extra day or two to get away.
I don't know what your special needs situation is, so I don't know if that's a game-changer or just makes their visit a bit extra-inconvenient. Others can advise you on minimizing the impact of visitors, hopefully.
Look at it like they are coming to stay at your place while doing a DC vacation. Don't look at it like they are coming to visit you and therefore you need to be in full-on host mode. Keep it simple, keep it easy. I've had long visits from in-laws who are, shall we say, not my favorite, and you just bite the bullet, don't put yourself out in an extreme fashion, and know that in a week it'll be over.