Threw sons first birthday...

So today my son turns 1. I have a small family and was trying to invite a small crowd my mother sister and my mother in law father in law brother in law. I sent out invitations and i am the kind of person that plans everything. I hate surprises and hate last minute ordeals. Im due in 4 weeks and 2 days and already feeling achey etc. Anyways last minute today i find out from my husband that my mother in law invited 6 of my husbands cousins including another baby to my house for the birthday and they didn't even plan to tell me i was supposed to be surprised🙁. Im really annoyed now becuz it changes it from homey and intimate to formal and awkard for me i dont even know those cousins well. Anyways im kind of bummed out now and feeling disappointed. Honestly is this over reacting? Perhaps its just me how would you all feel if this happened to you? Tia.

Ps my husband has a family of 600+ cousins most of whom i dont know but they are close knit.