We have tried carrying a kayak on an inflatable dinghy.. it can work but is awkward to set up. Carrying two would be difficult, they are beamier than you think as a rule.
In order to be able to sail and avoid interference with the kayaks we have always lashed them to the lifelines but outside the stanchions aft alongside the cockpit. They are light enough to easily manhandle them into position and not put too much strain on the stanchions and lines. The only time they proved a problem was in a big breeze and waves where we tended to put some water in them now and then. In the future on a day like that we'll put them up on deck somewhere.
Picture below to show what we do:
Mind you, ours are only 9.5 feet long - fourteen footers may be more of a problem.
But I think you'll find the hassle of lashing one or two (if possible) onto your RIB will be too much....