I used to put covers over the top of the nappies so they couldn't reach the tabs to pull them off. I started TT my DD2 at 15 months and she was fully TT at 19 months, but like PP said, it's up to you. Give it a go if you feel he's ready but most kids go through a pulling nappy/pants off stage. I wouldn't use it as the only sign that he's ready for TT.