It is loud, mainly due to audience participation, banging cutlery on tables, shouting and cheering, you are encouraged to be noisy.
Have a look at this to give you an idea of what to expecthttp://www.youtube.com/watch?v=fcnkv6ZVBCo
Both times we've seen it there have been spare seats in the auditorium, both times were offpeak seasons March and October.
I'm not sure how people manage with buggy's, pushchairs and sleeping children, the seating is in long rows, in thin aisles and they're quite steep, I don't think I've ever seen a buggy in there, it would be quite hazardous I think, with the waiting staff rushing around with hot food.
Possibly you might be allowed in the very top row as there's a kind of walkway behind you. Otherwise the seating is arranged so that it's difficult to get out once you're in - think cinema, but more difficult because the seats are fixed.
Not much help, sorry - perhaps someone else can help.
DH is telling me that there's an area downstairs where all the pushchairs were left, I didn't notice.
I found it when the question of how much English/French is spoke at the show was asked. I think it gives a pretty good idea of what to expect, although I wouldn't suggest anyone watches all of it before seeing the show, wouldn't want to ruin the experience for anyone.