Maybe call the organiser and ask how many dogs attend.

Tell them you are worried your dog may be over excited and i am sure they will put your mind at rest.

A decent class should let you just come and watch a couple of times so there isn't so much pressure to "perform" and you can see what the class is like. It will give your dog a chance to get used to the surroundings too.

Believe me you won't be the only one with an excited dog but that really is the point of these sorts of classes

Hope you go for it, they are invaluable if they are good.