Okay, making the case for Como!
Lots of things are the same as Garda - loads of ferries to get around (in summer) you don't need a car if you are staying somewhere walking distance from a ferry stop, you can swim in the lake and almost every village has a swimming spot/beach (mostly pebbles though, not sand), loads of cafes and restaurants, brilliant ice cream everywhere. I didn't have buggy age kids but I didn't experience any difficulty getting around - possibly some of the very touristy villages like Bellagio would be difficult with a buggy but I didn't go there so don't know. Most villages had level promenades near the water and there were plenty of families with buggy-age kids everywhere we went.
Things to do:
Our best one: Hotel Villa Aurora in Lezzeno has a beach club for which you pay 10E entry (or free if you're staying at the hotel) and get access all day to a water trampoline, kayaks, paddleboards, other floating kind of toys + sun loungers with bar, restaurant etc. We spent two whole days there - it's on the ferry route although there aren't a huge number of ferries so you have to plan a bit.
Crazy golf in Menaggio + lovely promenade
Villa Carlotta - fantastic gardens for kids to run around in and interesting not too big house
Villa Balbainello - more beautiful gardens, where they filmed some of Star Wars and a recent James Bond
Cable cars in Argengo and Como town
If you have a car, a short journey over to Switzerland and Lake Lugano (more cable cars if wanted).
Very modern multi-media museum of the end of the second world war (English options)
Wine tasting up in the north
Up in Colico, loads of watersports (sailing, windsurfing etc) because there's a constant breeze.
Hire a motor boat.
There was more, but that's the ones I remember off the top of my head. There aren't any theme parks or waterparks - that might be the biggest difference from Garda.