Went by the dealer today to inquire about getting an ATV for my 8yo and 13yo for Christmas. Was told that they could only sell me a 50cc for my 8yo and a 90cc for my 13yo. My concern is that I will be wasting my money on getting these smaller sizes and then having to upgrade within a year or two or the kids having no interest in them after a few months because they are too small. Are my concerns legitimate or will these sizes be fine and be able to last at least 3-4 years for each kid?