my son is 9 and weighs 90 lbs and I am looking at getting him a new atv. he is somewhat experienced and I let him drive my 350 wolverine around the yard in second gear. now I want to get him one he will use a few years. what do you recommend as far as size? im thinking a 90 will be too small next year he does have a little sister I could pass it down to but I want one he can ride at least 2 years.