Hey, I am a couple of years ahead of you! One thing you might want to think about is getting a beater bike for you and the kids. Mine is a old trek 3700 MTB I picked up for $75. I never liked trying to load a kid on a bike while trying to keep it from tipping over so I went with a cheap Schwinn double trailer I got used. When it broke I replaced it with a nice single trailer (now I am getting a cheap double trailer given to me by a friend who no longer uses it). You can always find something used on craigslist or FaceBook market place and then upgrade to something nicer later.
When my son turned 4, I purchased a wee-ride co-pilot hooked the trailer we had behind it so his younger brother 18 months could come along.
I used that rig for about 18 months. Then I realized my 5 year old was frustrated with the single gear. If I was going faster that about 12 miles an hour he was spinning. Going up big hills was too hard on his little legs. So, I purchased a tandem and got a stoker kit:
This coming summer the three- year old will use the wee-ride co-pilot and summer of 2023 youngest brother will be in the trailer.
By the time my middle son is old enough for the tandem; I hope older brother can keep up on a bike by himself!
Good luck!