Why are you giving them a risk of getting mumps with a 1 in 7 risk of meningitis?
Incidentally, my mother always swore blind I'd been immunised against rubella. It turned out that she'd got mixed up and meant my sister. As I conceived my children through ivf, they tested it beforehand and i was able to be immunised before conceiving. If I'd conceived naturally, i wouldn't have known.
If you're not going to get your children immunised against rubella as children, do make sure they really do know that they'll have to sort it out as adults before they think about trying to conceive.