Nice solution! I have a couple inflatables I'd like to do that with for the summer months. I hate to leave them out as I think the UV would deteriorate them at some point. I may have to borrow your design!
The afci breakers put off a fair amount of heat on their own. I was surprised by that as well. as long as they are just "warm" and not hot to the touch you should be fine.
Hey Mike, Like the others before me, I too am sorry for your loss. Tough deal no matter how you look at it.
On a positive note, the yard looks great! Well done.