Any nice flat areas at Berryessa?

we do 95% of our days on the delta, but when my sisters come out they want to bring the kids and go to a "real lake", so we usually do Berryessa. We generally launch from Markley Cove, I haven't even checked out any of the other marinas. Anybody point me in the right direction? Ideally would like to find some part of the lake that at least has some "decent" water for boarding...