Our older boys are teens and babysit our youngest, so we don't have childcare expenses. Even without those expenses, our view of "date night" at Disney is a little different from most. First, it's not usually an entire night - it's a couple hours either before or after dinner with the kids. As for signature restaurants, I think we've been to every signature on property with kids - most multiple times - except for Citricos. So we have an idea for what they are and what they are not to us. Our kids are always very welcome, the menus are interesting, the food quality is generally higher than at other Disney locations, and the atmosphere is more relaxing than the typical theme park restaurant. So with kids, the cost of a signature dinner is worth it to us. But not so much for a date night.
So instead, we go for fun and festive when planning Disney dates. We've done several 'mini dates' in the club lounge when staying club level, but I think our favorite dates are quick breaks at other Disney lounges. If you're in the Epcot, the bar at Il Mulino or at blue zoo are great for that. At WL, Territory Lounge is a wonderful spot. We also enjoy Tutto Gusto - the wine bar in Italy. La Cava in Mexico is fun too. But I think one of our favorites is Tambu Lounge at Poly - very fun and festive. So I think your snack date is a great idea!!!