For starters if he is potty trained that is awesome. It is common for boys to do it around 2 1/2 - 4 yrs. In my daycare the boys tend to be older when they potty train. As for the nighttime wetting. He is still very young and if need be stop giving him fluids a couple hours before bedtime and have him go potty before he goes to bed. If you need to use a diaper at bedtime that is ok to. Don't make a big deal about it to him. Staying dry all night is usually the last thing thy conquer along with bowel movements.
I wouldn't worry about it till he is almost 5 and still doing it. But kids are going to have accidents even when they are older. My son did it till he was 7. Partly due to emotional issues with divorce etc. But he is fine now.
I wish you the best and that is awesome you are going back to school.