If the dinghy is just an inflatable raft and not a RIB, you should just be able to strap it on the back rather than needing a davit for it. It would be very lightweight. That's what I did when I was using an inflatable right after I bought my boat (before I bought a more substantial dinghy).
If it's a RIB or hard-shell (or a heavier type of inflatable), then weaver davits are probably the way to go for the size dinghy you're talking about. If you want something really heavy-duty and mechanically actuated, you might take a look at some of the choices from Olsson Manufacturing: Builders of Boat Davits - Pioneers of Transom Davit Technology