That's pretty cool that your wife is looking for an instrument as an outlet. As a word of unsolicited advice, I would encourage her to pick out whatever she is most interested in and don't make it about your family band and be very careful to avoid pressuring her at all. I know you have the best of intentions, but it's really easy for things to get misconstrued in these sorts of situations. At least that has been my experience.

Good luck with helping her to find something she finds fulfilling.