oddball

Hi all, first post so please be gentle with me I am starting my son off trial riding, he has had a couple of hours on a rented ttr90 (little yammy) to get him riding. I have bought him a gasgas 80, he's only riden it in the garden so far (on the look out for a trailer), but it seems quite big and heavy for him, although he can touch the floor and ride around the lawn no problem.He's 10 in december and of decent height. Should I have got him a smaller bike to start with him being a complete newb?? Also what are the rules for competeing, I think he'll be youth 'C' which I think is classed as 80cc, but no mention of wheel size? Sorry if all this has been asked before but I have searched the net and have been finding info difficult to come by - even the smaller bikes there seems to be so many variations Anyway I need to sort him out so dad can get one Thanks Admin : feel free to move to another section if i've posted in the wrong secton