I think is it different from mixed race couples and their children. It would be difficult at first, but the wizards kept going and mixing with muggles, so it wasn't that difficult. I think that if a witch or wizard marries a muggle that something happens and they become aware of the wizarding world they can see the Leaky Cauldron and things like that. Especially if muggle parents had a wizarding child. They would need to be able to travel with their child and go to Gringotts with their child and everything.