Done a bit of Googling, these three braai spots seem pretty decent
Helderberg Farm, Somerset West
Situated in the picturesque Helderberg region, this farm not only offers picnic and braai facilities but also a host of activities for the whole family. These include gravel karts, laser shooting, strawberry picking and mountain biking.
Location: Klein Helderberg Road, Somerset West
Miller’s Point, Simon’s Town
An excellent spot for the family. Portable and gas braais are welcome, and there's also a tidal pool for the children, excellent snorkeling and a boat launching slipway. 
Location: Main Road, Simon’s Town
Berg River Resort, Paarl
Situated on the banks of the Berg River, this family resort offers something for the whole family. The donkeys and goats in the animal farmyard are always a big hit with the children. Other experiences include canoeing on the river, swimming, tractor rides and volleyball.
Location: R45 Franschhoek Road
The drive to these places isn't too far, and would be pretty scenic.