Keep it a fairly simple, short-ish hike. Almost think of it as an "overnighter" than a backpacking trip. build up to longer stuff later.
Stay relatively close to home. The trips I've been taking my wife on are up to are 30 minutes to an hour away.
Bring something fun: a treat, cards/a game, a book, something to do together when you're both at camp.
Carry the heavier pack, or take some of her gear. I'm not saying your wife or mine aren't capable, but again, you're easing them into this activity.
Make sure they use the more comfortable stuff to sleep in.

Talk and enjoy the time together!

This all assumes it's just the two of you going together....