Your goal sounds like a good one and I wish you all the best with it but I've been there before and I see a few possible problems you might run into based on your post.

These things stood out to me:

"she knows how to ride, but doesn't have much experience"
"I'm looking to get the family out"
"We don't want to invest money"

It sounds like you want to get your family riding together, which I believe is a very good thing, and that your wife might be interested in trying it out. However, it doesn't sound like she's very interested in the idea of riding. If she isn't interested in doing this on her own she may put some effort into it but then tire of the activity when the novelty wears off or the discomfort of a saddle or anything else comes up. Call me cynical, but I've found that human beings are unlikely to put real effort into anything unless they really want to do it or have no choice. Please don't waste time, money, and your hopefully blissful relationship by buying a bike that she may use a time or two and then hang on the wall or sell.

If you do get a bike for her I also recommend letting her pick out the bike she wants. She will know what feels comfortable for her better than you will.