If I nuke somewhere and an allie is moving into the radiation will it hurt his units?

Yes and if an ally is near a nuke blowing up they will get hurt too.

Alright thanks, one more question. If they are moving onto vacant land and I have a nuke going there will my nuke hit first and harm them? or will there untits arrive first and my nuke wont attack because it just became ally terratory? thanks

Turn order is random. It depends on who goes first.