My daughter turns 10 in September. I made her a 7’0" scaled down from my 9’0"and it was kinda thin. I’d suggest as thick and wide as your 10 year old can easily paddle. At that age it’s all about staying on the board. Just my Dad observations.
I like wide, as wide as you think he can easily pad. Width will create stability.
The thicker you go the more stable as well, but the harder to turn, climb on after a fall, the more the soup will tumble it, the harder to paddle out through white water.
My in process board for my 5.5 yr and 2.5 yr old is a rockered out 5’9"x16"(n)x18"(c)x15"(t) longboard. The rocker idea is that it will be easier to turn. It is thin, only 2" but the idea is it is a push in board so I want it to be turnable. It does not need to catch waves. It is a 50/50 softrailed board with no sharp edges. It is going to have a thruster rubber edged safty fin set to make surfing all the way into shore easy. (that was a tip from Kieth, his girls ride their board all the way to shore)
I’d be thinking in the sub 7’ range with a little extra tail kick to make it easier to turn. Maybe a little extra nose rocker to help with the perl factor. Shape in from the bottom. Thin nose will reduce weight and thin tail will help start a turn. A little belly roll will help both turning and stability. Oh 7’ does not seem unreasonable though.
all epoxy, multiple wood lam. It would last until your son’s adulthood and could be passed down to your grandchild if properly cared for. Don’t forget to use epoxy resin in your project!
18.5" nose and 14" tail, rocker suited for Hawaii. It’s a board style is from the early 90’s called the “missing link”. This board is for an adult but would be a perficet longboard for a child.