I do the same thing with my 10 and 11 y.o., and race for fun with both of them. I bought a Hobie 16, and you cannot beat the combination of simplicity, durability, and price! Your combined weight should not be a problem (the minimum H16 crew weight is 285, so you are not too far off that, if you would want to do some racing), and if the two of you want to step up to something bigger after a few years you can likely sell the boat for what you bought it for, or let your kid sail it! BTW, my boat is at Gulfport Yacht Club, come by if you want to see if a H16 would fit your needs.