I don't know if they have one table that can accommodate a party of 16 (although it looks like a number of them are infants). You'd probably be divided among 2 tables alongside each other.
My kids LOVE the Biergarten. Love the food, LOVE the band. They are now 8 and 5, but we've been going since they were toddlers and it hasn't diminished their fondness for this place. It is the one place they ask to go back to every time... and it doesn't even have any characters!
Order the LARGE beer, I just read somewhere else on the boards that you can get a "to-go" cup at the end of your meal (although, I've never needed to ask for one!!! )
And yes, seating is in tables of 8 so in all liklihood you will be split onto two tables. This makes it a lot easier to get in and out for the buffet and dance floor than if you try and pack yourselves all around one table with the babies.
As for the shows, I don't recall specifics, but I will say that whenever we eat there we tend to see it twice, so I wouldn't worry too much about the exact schedule.