What's with this 20 year hiatus? It's like the windsurfing world stopped around 1990 for a whole lot of us and we're all coming back again!

Good stuff.

I've only just come back early this year with around the same 20 year break. I chose to go with longboards this time around as I want to get back into the surf, as where I left off, it's windsurfing's version of mal riding (slow progress though). This style of board can be an option for you too instead of short, fat and wide (SFW). But....
The modern SFW boards are quite floaty too and would be easier for kids to handle as the boards are very stable...I've been told. Are you in Sydney? If so contact one of this forum's sponsors www.windsurfnsnow.com.au and I recall they had a used modern HiFly beginner/intermediate board for sale a little while ago, it has a retractable centreboard which offers even more stability and allows you to point higher and get home if you stray too far downwind. They can put together a package for you too out of their used range if you choose to go that way. It would save you lots of time in trying to re-educate yourself with what gear is suitable.
Modern gear has become more technical, in description anyway, and there seems to have been more disciplines than back then so it can be complicated and confusing if you don't do your homework first. Apart from "beginner" boards also look at large volume styles as another option, over 150 litres to 190 litres should do the trick. Dufour Wings and TC Runners were both around 220 litres as a reference. You don't need that much volume nowadays as the width can make up for it.
If you come across sails that are suggested as suitable and seem too large eg. 6.5-7.0, believe them as they are not as powerful as the same size sails back then and are more forgiving. They spill excess air via the top of the trailing edge of the sail but to do this the sail requires more area, hence the bigger sounding numbers. They are appoximately 0.5m2 larger nowadays.
Avoid cammed sails at this stage too as they require a little more fiddling and set-up knowledge and not very beginner friendly.
Like you the first thing I noticed when I started my research was the shape of modern boards, I still think the SFW ones look weird, particularly the "Formula" racing models.
Good luck with your search.