How far ahead do you need to make reservations for a Saturday-Sunday camping trip for a group of 20 people? And do they have group discounts?

I'd say a year out

Not sure, call them and ask

Ur only allowed so many people on one site so you would have to get multiple sites. And no they do not have group discounts. Most people do it the year in advance especially if they want their big group to be all together, but you can try cuz it especially depends on what time of year you go.

We only have a party of four and stay for 2 weeks. But, to assure we get the spot we want and the dates that we want.. We make them 1 year in advance. Not to say you might not get lucky. Good luck!