I got my kids (twins) balance bikes before they could crawl and left them in the living room. They were playing with them when they crawled, push-biking with them when the walked, riding crazy down hills at 2 and 3, riding pedal bikes at about 3.5 and so on.
Gave the push bikes to my bro-in-law for his twins. He got them tricycles too. They pretty much want no part of the push bikes, just like the pedaling of the big wheels and trikes. Learning nothing, four years old now and I figure won't ride a bike until they're 6, 7, or 8 at this rate unless I teach them.
Nothing wrong with that either, I just think it's better/easier to skip the whole trike to training wheels thing and get right to business.
When it's time to move from a push bike to a pedal bike, it helps immensely to find a little bike that is a fixed gear rather than coaster brakes. That way the kids legs have to pedal, and they learn that. I drilled two holes in the rear sprocket of my kids bikes and zip tied the gear to the spokes so it would always pedal when the wheels turned. Very irritating to be pushing the kids and they keep locking up the coaster brakes and think it's funny.
All my opinion. They do have a ball on trikes, but I've had people ask me how to teach their older kids to ride without training wheels.
Against wally-world opinions on the forums, you can get a balance bike off walmart.com for 29 bux. At least you could a handful of years back when I got mine.