I know that is rough. Don't let it ruin things for you. Perhaps you can do some creative fun. I don't know how old your kids are but mine woudl rather sit and water color w/ me than go somewhere. They'd rather I read to them from a big kid book (last winter we read inkheart) than go to a movie. As for gifts. Make them. Do you do any crafty things? Do you knit or scrap book or write poetry? Are there online courses you wanted to take and never had the time? You can catch up w/ friends on face book you can get some serious reading done.
As for the cleaning - do you have any good friends? I"d ask them for help and let them know in return you will do xyz - maybe clean for htem, keep their kids for a weekend, or whatever. If you can do nothing in return ask anyway. Friends, true ones, really do want to help how they can. A good friend of mine was VERY ill for a long time and I did her cleaning. It made me feel so good to do something for her. I was so honored she let me.
and finally, you sound seriously ill. Your family will be happy to have YOU and the importance of material objects as gifts as well as the state of their house will not be important to them.

Hope you feel better soon.