Actually, it's 10 people per site. Two adults and 8 children are included in the price of the site. Any adults over two incurs a $2 per night charge.
As far as number of tents, it doesn't matter as long as they fit within the dimensions of your sand pad and driveway. You can not set up anything outside the "square" of your site. (Staking lines outside your area is OK, but nothing can physically be on the ground outside your area). You also cannot move your picnic table outside the "square" to make more room for your stuff.
I hope this helps.
Carol