How far do you push

Yesterday, Y had another school trip, which I agreed to chaperone. I have to admit that even though I agree to go on most of these trips, I really do not like them at all. Part of the reason is the logistics- get a babysitter for M, give up on a morning of errands, etc. But mostly it is just because I know Y will not enjoy himself.
You see, Y absolutely hates and detests large crowds and noises. He does not like performances of any kind and will only make an exception for Uncle Moishy. The last two trips the school took involved the circus and a 3-D presentation of the planets at the Museum of Natural History.
So the trips went something like this: Enter the auditorium/circus- Y freaks out and yells "no", trying to run out. Bring him back and tell him it's okay, that it's not scary and I am with him. Put him on my lap and put on my fake-enthusiastic voice: "Look it's the horse/magician/moon. Isn't that exciting? Isn't it fun?" Sit for five minutes. Loud noise on stage. Y freaks out again and makes a run for it. Go outside, take him for a walk. After 10 minutes, force him to go back inside. Repeat until he has had it and refuses to go back. At which point we wander aimlessly outside for the next 30 to 45 minutes till the performance is done. Then we rejoin his class, having gained absolutely nothing from this trip except for frazzling my nerves.
So I did not have high hopes going into this trip. We went to Hunter College to see a performance by the Paperbag Players, or something like that. My apologies if I got the name wrong. Of course, he was very excited to go on the bus. The trouble started when we got to the theater. He took one look at the seats and stage and walked out. After some coaching and encouragement, we settled into the back row, close to the exit. When the lights went out, Y had another freak out. For 20 minutes I was able to convince him to stay inside. It was a pretty low-key show so it wasn't too loud and there weren't any bright lights. Then the scary octopus came on stage. That was the end of us. I felt a little better, that when we walked out, another little girl was outside crying about the octopus...not that I was happy that she was crying, just that my kid is not the only one.
So off we went for a walk. We found a corner store and bought cookies and snapple. We enjoyed our snack and then I convinced Y to go back in for the last 10 minutes. So I guess, 30 minutes out of a one hour performance is not too bad.
I still end up feeling crummy by the end of it. And I wonder what the right thing to do is? Should I keep going on these trips and push him to participate, to sit, to stay in just a bit longer. Or should I just accept that my child does not like performances and really will not be too damaged educationally if he does not go on these trips anymore. Maybe, we should just take a mental health day and stay home on trip days. Both he and I will probably enjoy that more. Always the balance of figuring out how much we can challenge and prod our children, and what is too much.
In any case, I have decided, that for the next trip, whether Y is participating or not, I am definitely not going. If he will be outside anyway, then let it be his teachers taking him for a walk around the premises. I am officially done :)