3.5 year old potty trained but still has accidents..normal?

I potty trained my son after he was 3. I was just going through a lot personally and put it off. Plus he wasn’t showing interest. Once we did it it was fairly easy.

He’s going to be 4 come September. But still sometimes has accidents. We have yet to have a poop accident, just pee. It’s usually in the car or while he’s watching.

We still do diapers at night as he’s still waking up with a wet diaper and sleeps 12 hours - so I know he’s just not ready to ditch them yet. He will poop in the diaper at bed time too.

Do you think him wearing diapers at night is slowing this down? Should I stop them all together? Is this normal? What do you think?