Should i be offended...?

My boyfriend's 21st birthday is coming up and he's super pumped about it. We have been dating over a year and have a almost 5 month old baby together. I'm only 20. His mom has planned this elaborate surprise party for him and didn't include me in on anything. She is planning on taking him to a club with his brother and best friend and then to bars to drink. Should I be offended I wasn't even a thought?

Ps. He has told her he wants to celebrate with me but she keeps telling him she just wants it to be them...? Weird or not.??!