Don't know of any beach launching in Suffolk at all. Options for slipways are a little scarce in Suffolk but Suffolk Yacht Harbour at Levington is good all tide. Campsites nearby try Orwell Meadows I think it is. If you want a beach for the kids to play on then head out of the Orwell and hang a right to the Walton Backwaters and go to Stone point at the entrance. If the weathers good there will be a dozen boats anchored off with the kids playing ashore.
Another option could be southwold but thats a case of beach seperate to launching and ribbing cos you cant beach your RIB there. Also very strong tides and dont be there on an onshore wind
If you want to try Essex then Brightlingsea, Mersea or Bradwell could be of interest. Beaches nearby and sheltered water in the Blackwater estuary.
