Family of 4 traveling through Thailand

You'll be safer driving yourself. Thai drivers are mostly fucking maniaks! M

@jackfish.
Welcome to the forum....

Self drive would be the way to go. Bangkok may not be the place to learn how to drive in Thailand. Have you thought of basing yourselves elsewhere, some place quieter to learn the ropes.
Perhaps Chiang Mai up north to give you access to northern Laos and across into north Vietnam.
Ubon Ratchathani near southern Lao border is okay too. Access there into Laos, Cambodia, South Vietnam.
Udon Thani gives you access into Vientiane Laos.
Or one of the cities in central Thailand.

Thanks for the advice. We've been to Laos before but that was without kids (21 years ago now). We recall it was quite rough back then but with 2 teenage boys ready to try it again.
We liked both Udon Thani & Ubon Ratchathani so quite willing to consider these options.  Also got around in either a van or pick-up without any trouble but have heard times have changed & the roads have become even more busy / scarier than 21 years ago, also the prices of renting or buying a vehicle have skyrocketed.
Where would you recommend sourcing a reasonably priced wheels?

I would do a Google search, say, 'expat cars for sale Thailand' or something similar.Long term rental costs would be rather pricey.
For living costs try www.numbeo.com

Or when you decide which city you are going to settle in check if there is an expat club or community there to help you find a car. There is such a club in Chiang Mai and may well be one in Ubon or Udon Thani. This may influence which place you look to base yourself in.

I too support the self drive idea so maybe you need to save a little more money so you can afford a reliable vehicle.  Some adjust well to driving here and others do not.  Maybe in a couple of years when your kids are actually teenagers you might have enough money and have figured out visas, learned some language and developed a better plan.

Cheers villagefarang, out of the 4 of us I'm the only one who does not speak fluent Thai.
My wife of 23 years was a school teacher in Yasothon, I used to work for her older sister who was a school principle. I was a teacher myself for 4 years in NE provinces.
I can legally stay in Thailand on a retirement visa, my wife & kids can stay there as residents.
We have purposely chosen not to have a "better plan" as too many times we have visited other countries and "planned" things and not enjoyed ourselves as much as we do when we "go with the flow".
Thanks anyway.

It would have been very helpful to lead with the Thai family info.  With that additional information your plan makes more sense.  Work your family connections to see if someone might have a car you could use at a more reasonable price.  Even if you have been away for a while Thai connections are always better than Farang connections.  Hope you have a great time going with the flow.  That has always been my approach to Thailand.