Best airline for no questions asked kayak travel is United, make sure non of your connecting flights are small planes or with other carriers. I have boats for rental and custom as well as all inclusive trips for paddlers of all levels, my company is Endless Adventure International
and our guides know the area well for all classes of paddlers including class IV/V. Abe H of Boof Sessions also rents boats and has a pretty good group of budget kayakers hanging out in the Baeza/Borja area.
Also, don't forget Baņos on your list of kayaking destinations, TOPO is a class V classic and the Pastaza is a great big volume option with three sections, also park n hucks as well.
have fun! would be great to paddle with you in this epic paddling destination.