What to do about an unexpected house guest?

I live with my BF in a one bedroom apt. and I just found out his cousin and her three sons (all under the age of 5) will be staying with us from Wed. to Sun. for a family event that I planned for Sat. Im not a huge fan of her although Im civil so my boyfriend didnt let me know she had called and asked to stay with us until today. Other family in town will be playing host as well and Im glad she is coming to support my BF but her family drives me crazy! She lets her kids run wild all the time and it will be very cramped with everyone there. Also I have several other events in addition to the grad party I planned for my BF- a wedding and a friend's grad party- so Im not sure what to do with her as my BF will be working too that week at least until the weekend. I dont want to be rude but I dont have time (or the patience) to play host to her. How do I handle this situation without going nuts or coming off as a jerk?

Yeah Im annoyed at my BF too for witholding important info on me and putting this extra stress on me. But he has argued that my mother made a rather dramatic stay at our place during winter break and I let her stay without consulting him. A low blow considering I did apologize profusely but he has the get out of jail card on this one...damn. So I feel a little stuck on hosting her and her family but not sure how to keep my sanity.

I'd say your BF is a real jerk for making plans without your approval. Bed the guests down in the floor in the living room, make a huge pot of spaghetti, and ask the "guest" to help out with the chores. Don't play host, it sounds like you are busy, let your BF deal with it.

I would ask your BF's family if you could switch relatives for someone you get along with better and without all the kids seeing that you have such a small place and no time host her. Also that was really rude of your BF to let his cousin stay without consulting you first, he is the one coming off as the jerk for giving you un needed stress.

I agree-get them a hotel room reservation, and use the BFs card to pay for it. You can gently explain to the cousin how much more comfortable they will be with their own bathroom, and enough beds for everyone, etc. Have them over for dinner, and play the hostess then. Mothers are different.

Can you just go stay somewhere else for those days? Let him deal with her and the kids, go stay with a friend or other family and just say that you wanted them to have more room. That will show him when he has to deal with it by himself.