If you and your son are both planning on flyfishing, I say get a two man pontoon or a raft. Nearly impossible for two people to flyfish out of the canoe.
Heck, one person flyfishing out of canoe (especially if they have to standup) is tough for most. Adding the shifting weight of someone else just makes it that much tougher. If your just using the canoe to transport you to the next wading spot, then you will have no issues.
A small trailer makes loading so much easier with either boat choice.
A pontoon like a fishcat 13 can also easily be ran solo.