Perhaps something that takes advantage of the tourist traffic and the current economy, where people don't want to spend a lot of money unnecessarily? Maybe a web-based guide with reviews of lesser-known "bargain fun" tourist attractions and inexpensive, family-friendly restaurants in the area? You could sell advertising on the site. You might also be able to get the restaurants and attractions to pay for "enhanced" listings.
Or maybe lead group excursions to some of the "bargain fun" destinations. Or both.
Or perhaps (depending on the type of tourist trade the area attracts), go for the high end tourists who still have money to spend, offering some kind of highly personalized "concierge" service or something along those lines.
I'm sure your wife's daycare has its own regular clientele, but maybe you could put your heads together and come up with a way to provide "drop in" daycare service for tourists (and locals, too, maybe?) who want to visit a "grown up" destination but are traveling with younger kids. Might be something y'all could do in the evenings after "normal" day care hours, but when people might want to go out to a fancy restaurant or to see a movie or something like that.
The main thing is to find something you find interesting and fun to do. It's really, really hard work to get a new business off the ground, but when you're working on something you enjoy, it doesn't seem like such a tough slog. You're much more likely to put in the time and effort required if it's something you love.