My wife now (and I started 5 years ago where you are - 2 boys are 6 and 4 now) bikes the boys to school, will bike to the store because it's easier than driving, and is interested in starting some recreational solo riding (Boy 2 now in Kindergarten). We had a croozer double stroller/trailer that went everywhere until the youngest moved onto a Burley Kazoo. (Skip the cheap 3rd wheelers. Burley is worth the $$)

My wife has a hybrid. Started life as a Norco entry level hybrid - 3x7, alvio, flat bar. I bought an aluminum cyclocross frame used because I was tired of lugging the low-grade steel frame around (I love steel bikes - but not boat anchors). I actually don't think the frame was ever built up, but I got it for $60. Had almost exactly the same measurements as my wife's step through frame but with a normal slope top tube.
She was happy with the bike, but was ok with me swapping the frame to make it lighter.

This year, I upgraded her to 9 speed - I got some 9sp shimano trigger shifters from a motobecane mountain bike I picked up on trash day, sunrace cassette from MEC, $80 wheelset & $35 crankset from pinkbike and some $12 brake levers from the LBS parts bin - She didn't notice that I'd actually replaced her bike until I mentioned it. Only things left are the brakes, handgrips & seat. What with the parts I've sold on, maybe a $150 total in upgrade (and I haven't sold any of the components from this year yet, just the frame from last year)

Then she agreed to come with me to the Toronto International Bike show (very nice experience BTW if anyone involved is reading) and test-rode a Specialized AWOL. Discovered she actually liked the drop bars (riding on the tops), and it's quite a relaxed geometry, and comes stock with 700x42's (she's had 35's and 38's), so now we're shopping adventure/gravel/touring bikes.

Basically, let her discover that it's fun and convenient, nudge a little bit and provide decent kit. If you're in a location where biking makes sense, you'll probably end up doing it. Looking back I wish I'd sprung for a wike box bike or a cargo bike / xtracycle when they were younger - would have been worth it compared to some of the messing around with stuff that we did.

Good Luck!