I've always resigned in person, with a cover letter that way it's in writing you can personally say I quit then hand the letter for the rest. Maybe bring DD along just before nap time so you have an excuse to leave lol.
OP you financially may not need to work, but I'm a big believer in keeping your foot in the door. I know a lot of women who quit completely then spent a few years out of the workforce and are now struggling to get back in now the kids are grown up. Could you reduce hours or take unpaid leave ?