Years ago, my father had a Yamaha 4wd Timberwolf with high/low range transmission. He loved it! It was a really good compromise between size and utility. He eventually moved up to a Big Bear, but I believe he always missed his "little" bike.
I could go one further, & ask for a youth UTV along the lines of the Polaris 170 RZR. It could have 4wd, and the Recon drivetrain. Teach the kiddos how to shift, and it could haul them to adulthood. Sort of a beginner P500.