Im having similar issues at the mo and my son will also be 3 in May. He is also dry during the day but still wetting at night. For months now he has been getting really upset putting his bedtime nappy on cause he says they are only for babies, In the last fortnight i have struck a deal with him, he doesnt have to wear a nappy so long as he gives up the juice cup he takes to bed. He now goes to bed with either just pants or a pull up and i have put the pampers bed mats on his bed, also doing the previous suggestion of taking him to toilet approx 3 times in the hour leading up to bedtime, I have since had 2 dry nights although most mornings he is wet but the mats protect his matress, but its a starting point and he is much happier, i however think my washing machine is going to burn out!!!