I'd look at other cloth options. Diaper pins are pretty old school! Ours have snaps. To get a diaper off my daughter would need to undo 8 snaps (4 on cover and 4 on cloth diaper itself)...which are not that easy to unsnap. Most also have Velcro options which could work.
Also put a onesie over the diapers so he has to get past that to even get to the diaper.
That said, most kids will slow down and thin out when they get mobile so you may not need to worry!