It'd be fairly reasonable, I think, for them to be entirely estranged. Junior did, after all, completely fail his NEWTs. Shocking behaviour, especially when everyone had such high hopes for his future.

So if memory modification isn't possible, I think we could get away with it. I doubt they'd be that thorough on some random chap running a shop, although, these days, goodness only knows how much they're spying on us. Better safe than sorry, if we can get to him.