Hi - I don't know if pianos are still made with wooden frames, but most nowadays would be iron framed, or cast metal of some sort.
Metal makes them stronger, and therefore keep in tune longer. Wooden frames can warp, and be more sensitive to environmental conditions, so might not like central heating. Also, in a worst case scenario I guess they could suffer from woodworm, but then I guess the wooden cases and other wood parts of metal frame ones could as well.
If the price was that good, won't it at least do to start the girls off for a few years? Then, if they get really good and are taking advanced Grades, maybe you could upgrade to a better instrument.
Strangely, you don't seem to have mentioned what it SOUNDS like! Did you try it? Do ALL the notes play, without any buzzes or rattles? Do the pedals work effectively, without creaks and groans? Do the keys go down smoothly, without any feeling stiff or as if they are binding on adjacent notes?
Easy to be wise after the event, but a pity you didn't take a pianist or music teacher with you to help check it out.
And of course, there are also electronic digital pianos, which these days have almost the 'touch' and sound of a 'real' piano. Digitals can be hooked up to computers for multi-tracking, or to sound modules to give thousands of additional sounds.
(I normally only 'post' on Primary Education, as I worked in schools for twenty years, and I've only recently come across this Music area.)
I hope it all resolves satisfactorily for you all.
Please help. We know nothing about pianos but have just bought a wood framed one for our DD's to learn to play on. It looks beautiful, was a really good price from a lovely retired couple and they had it checked out by a local reputable tuner who said it was in great condition. However per the internet we have made a big mistake and having called a couple of tuners they have expressed 'concern' about it being wood framed! Have we made a mistake - any comments appreciated before we spend even more money moving and tuning it!