I find this question very bizarre, what's the hell is wrong with riding a bus with kids? Why is it "more difficult" or any different from just riding the metro yourself? I rode the bus regularly from birth until 7 or 8 when my parents bought a second car and still rode sporadically with family or baby sitters from 7 or 8 until I was a teenager. I started riding again by myself or with friends as a teenager to go places and also rode the bus to work until I bought a car at 17. Riding with children is exactly the same as riding by yourself, except you have children next to you. Children under five usually ride for free too, at least they did in my city.

As far as sticking kids on bikes, you got many options:

https://www.oregonlive.com/portland/index.ssf/2011/01/oregon...

https://www.youtube.com/watch?v=f3SP1Y98KhQ

https://www.survivalistboards.com/showpost.php?p=3482606&pos...