I don't know how to vote, but absolutely I'd be happy for my child to be friends with yours. Why wouldn't anyone?
If the parents weren't happy about it I'd think they were the ones with a problem, frankly.
For what it's worth, DD was privately educated and we had/have a big house and some land (not Georgian listed level, though) plus a holiday home, etc. but would never have thought anything of DD having friends at a local comp from families who were less lucky financially. Quite the opposite, in fact.
DDs loveliest friends at school age were one from a not at all wealthy family who's relative paid her fees at the same school, and another who was at our local high school whose parents we became - and still are - very good friends with.
Think about it another way, OP, if you came into some money- won the lottery, big inheritance, etc., would you want it to change your DS's friendship circle?
Nice, decent people with money are no different to nice, decent people without money. Or at least they shouldn't be.