Homecoming Dilemma

Hi! So I'm 16 years old and a junior in high school. Homecoming is coming up in late October and I'm torn on what to do. My boyfriend and I agreed that we would go together but the problem is that we are in different friend groups. I made it clear to him that it was fine with me that if he wanted to go with his friends then I would just go with my friends separately but if he wanted to be together we could go out to dinner just the two of us (were not planning on going to the actual dance). He then said that he wanted to go with his friends but he wanted me to go with him because if I didn't then people would be confused as to why his girlfriend isn't there and that he really wanted me to go with him, kind of making me feel guilty (I don't really think anyone would notice though). Now the reasons why I don't want to go with his friend group: 1. there will be 70 people there and for someone who is introverted, that is very overwhelming 2. I don't really know his friends and I'm very shy so it is difficult for me to contribute to any of their conversations 3. it is more of the cool, intimidating people at my school which is intimidating for me 4. on the party bus they will be drinking which really isn't my scene 5. last year this bus got suspended from school for drinking. Now reasons why he can't come with my group: 1. My group is all girls so he would be the only guy there 2. he doesn't really know my friends all that well and thats all. My friends were just planning on going out for a nice dinner which sounds so much more appealing to me than drinking on a party bus. All my friends said that if they were in my situation, then they would go with him and my mom said that its my obligation as his girlfriend to go with him. This is causing me so much stress and I don't know what to do. Please help!