DS won't go to the toilet at nursery

[MumOfAToddler26]

DS is 3.5 and currently doing a couple of mornings (3.5 hours) a week and won't go to the toilet at nursery.
It's not a big deal as he is only there for a few hours so he goes as soon as we get home. But after Christmas he will be doing a full day so he will have to go.
When I said to him about it he gets upset saying he just wants to wait until he gets home to go for a wee, and I said why? He said because I don't want anyone seeing my Willy 😂
Is this a common thing and has anyone had any ways to over come this?
I said well just go to the toilet and ask the ladies to turn around while you do a wee, the thing is he can pull his pants and trousers down himself and go for a wee on his own but struggles to comfortably pull them back up again so would need help making sure they were pulled up properly.

by january he may be able to sort himself out anyway
but talk to the staff at the nursery and explain that he may need help with his pants/trousers after, but he wants to go for a wee on his own we always are about when our nursery kids have a wee, and always ask and respect their decision if they do/dont need a bit of help