Never done one in a car mate, I only have a Scenic lol
There are 3 groups, novice,intermediates and fast group. If it's your first one I would definitely drop in the novice group. If your too fast they will move you up to intermediate anyway as they put timing devices on the bikes to make sure fast people aren't in the novice group and looking like heroes and slow/new people aren't in the faster groups holding up others. It's a great idea to be honest and improves safety if your riding with people that lap roughly the same.
As to the Cans,if they have baffles fitted then yes they will but if they don't then it's doubtful.
I've just got the big chunky standard can on at the moment.
You can get removable baffles/decibel killers anyway and they just slot inside your can and attach with a very small bolt.
You get a right mixture of folk who come with vans,tools,tyre warmers,stands,microwaves and the business.....and then you get the guys that just ride there in there leathers and borrow a spanner to take off their mirrors.
What I can say is everyone I've ever met on a trackday has gone out of their way to make a newcomer more comfortable/confident.
Check out Focused Events website and I think they have a Link on what to expect on the day.
Donington is great as there are about 4 bikes to each garage/Pit....so plenty of room.
Hope you can make it!
Steve