I recently visited Isaan for a second trip to see dinosaur fossils and museums, and visited a space museum / plantarium. The first visit was to Kohn Kaen, the second to Roi Et, with one dinosaur museum a bit out of both locations.
Dinosaurs were in Thailand those 65+ million years ago as far back as that goes, including a Thai version of a Tyranosaurus, and today there are fossils to be seen and museums that cover that scope. The museums are pretty good, if not exactly the Smithstonian. One main difference is that they rely on complete skeleton fossil mock-ups instead of housing the incredibly rare excavated complete sets. Ancient versions of early hominid species (homo erectus and such) were also here, with limited fossils on display related to those, and plenty of description to inform kids of that natural history.
All of it is more completely covered in English than one would expect; a non-Thai speaker could enjoy and follow most of the dual-language content. Obviously not all of it, since at some point some display videos would use spoken Thai without subtitles, but they've made an effort to present it all in both languages (with probably essentially no coverage in any others).
I wrote blog descriptions of these visits, and I'll include direct links to some of the places I visited in the following as well. The blog is really a tea blog but I cover travel related scope in some few posts, like these. The Kohn Kaen fossils are arranged in parks more than in the other site, in addition to the one main museum with a walking loop in the main park to see the main fossils that covers 4 kilometers or so. The terrain in that park is hilly, so not ok for elderly or physically challenged visitors, but children could do it, given enough time to cover the ground. We visited Kohn Kaen in January and the weather was just perfect for a short hike, but of course during lots of other times it could be a bit hot or rainy instead.
One more tip, related to housing: Hop Inn is a newer chain that offers inexpensive hotel pricing for completely modern, brand-new room facilities, if a bit basic (no restaurant), with locations in both cities. I probably shouldn't mention pricing here but it's well under 1000 baht. Aside from travel concerns (Thai roads between Bangkok and Isaan are a challenge, and flying brings up a few other challenges) a trip out that way needn't cost much at all.
Links, to my blog posts covering details and direct to museums and parks:
(Roi Et trip) http://teaintheancientworld.blogspot.co … ewing.html
(Kohn Kaen trip) http://teaintheancientworld.blogspot.co … n-and.html
(dinosaur museum details--no page available) http://th.sidolocal.com/shopping/10143/ … -sirinthon
(planetarium / science museum page) http://www.roietsci.com/
(planetarium / science museum facebook page) https://www.facebook.com/profile.php?id=100012436891390
(Trip Advisor link to Kohn Kaen museum, really well outside that town) https://www.tripadvisor.com/Attraction_ … vince.html
(Thai official travel site for Phu Wiang--Kohn Kaen area--dinosaur park): http://www.tourismthailand.org/Attracti … -Park--853