Kami said..
Hello, you can drop down in size like he is doing good on 6'10''
Actually, I wouldn't recommend going to these kind of 6'10" (somewhat narrow nose) at first. Could be too much of a step down.
Something in the 7'-8' range with a wide nose, and a tail adapted to your waves (narrow for power, wide for mellow), with a fast rocker will be fun and easy.
I would recommend a "mini noserider" shape in 7'8"-8'0"x29. My daughter has one (Gong NFA 8', but a lot of brands have similar boards now) and everybody that tested it got a smile on their face: super easy (wide nose & tail), glide feeling of a longboard (rocker), but carves like a (retro) shortboard (shorter length, somewhat pulled in tail, and generous tail rocker). They are much easier to ride well than Tomo shapes, as they are not as sensitive to the rear foot placement. If I had to take only one board in a trip, it could be it.
Here is a video tour of the shape to see the design features
A vid in action:
The same shape in 7', by the same rider (Xavier Leroy) on the vid posted by Kami.
Again, I took the Gong line as an example, as I know it best. But many brands have quality "mini mal" SUP boards.