As first time cruisers this is a good thing not a bad one. I want quite laid back locations that are not packed. Although from others it sounds like they are more specific hours some places might fill up more.
I would say watch the vlogs that are out there for
Disney cruise. If the shows and activities are not for you that's fine. Disney needs to stay Disney and let others fill that casino void.
I plan on just bringing my Nintendo Switch if things get "boring" I can easily pop out the switch and play a party game in one of these low attended lounges. Heck random people might even want to join as well.
If I wanted to gamble I would personally be in Vegas where I have options as I wouldn't expect a
DCL casino to offer much of variety likely and it's very unlikely to have things like poker.