B.B.
My 2 y/o son seems to have the bladder capacity of a 20 y/o! :) We have had horrible night time leaks!
I started using Huggies Overnights and haven't had a single leak since, some mornings the crotch of his jammies might be a little damp but nothing that requires middle of the night bedding/clothing changes!
I've also heard of some moms using a Maxi Pad stuck to the waist inside the diaper - but I haven't done the math to see which method would actually be cheaper. But since the Pads have adhesive and are soft, it makes sense.
Good luck!! :)