We bought a graco nautilus car seat for our son to sit in in my parents' car. He's nearly 2 and has only been in it a dozen or so times but has already learnt how to unbuckle the harness. I'm not impressed- he's too young to understand that he needs to keep belted up. He's had no luck in our britax dualfix so clearly the graco buckle js not very toddlerproof. We've had it about 4 months- can I realistically take the seat back for a refund or do all kids figure this out sooner rather than later. What do I do to keep him safe?