I LOVE seeing my kids and yours having that level of fun !
One paddling dad to another....a suggestion......
purchase a mini max, puma, class raft.
1 ....VERY EASY to talk to each other....my son and I have had some wonderful conversation on river, because it is easy to talk, when you are side by side !
2......fun for the whole family ! 2 adults + 2 kids is a very safe and ride...2 adults can eaisly control the boat.....but your boy looks ready for a paddle
3....very small and light boats for strorage and transport.....heck my mini max will almost fit into a xl duffel bag from walmart,
I have had, and still have great fun on the river r2ing with my son....he is now 17....calling paddle comands.....I have similar photo as yours....mine is of him, in a duck....simlar look of escatsy on his face ! he ran all of gates of lordur, one summer all 4 days in that duck ! ...he never got into the raft...age was like 10-11
Glad your young one is stoked on the water !
Kayaks are Great ! ... just keep your mind open to r2 rafts...they have many benifits for father and son teams.