My two 10 year olds have been learning on a few boards with ezzy 2.0 and 2.5 sails. A 10'8" JP all rounder sup, a starboard start with an old fin for the centre board and last weekend on a 151L starboard go with the small fin underneath. They both did well on the starboards but without a centreboard/fin the sup would not even sail across the wind with the small sail, would not tack either, so they learned to sort of gybe. The borrowed start (thanks Geoff) gave them a nice wide platform and would sail upwind, so most the time they were able to sail back to where they started from, and I didn't have to rescue them. They managed the go as well just not as stable, but on flat water its good. Used a 42 cm fin in the go and a 6" fin for the centre one. Next time I'll try them with out the small fin and see how they go.

If you get it for the right price I would recommend putting a fin box in the centre or Bunnings sells cheap suction things.
As a side note to kids learning, I read on here some years ago about towing them along behind another board to give them the feeling of going fast/planning etc. I did this last xmas holidays. Used a longboard(can't remember what its called) Tied rope from rear foot strap to the hand hold on the nose of the start and went sailing. In about 15 knts, the young fella comes in stoked saying I never knew it could feel that fast.( I don't think we were planning, but definitely going faster than the ezzy 2.5 had ever been before).