Puy de Fou -
if you pre-book tickets online two days before you get a small (10% I think) discount. If you are doing just one day - arrive early so that you can fit everything in.
I wouldn't bother with the cinéscénie (night show) as it will add costs and will make for a tiring day (also although it is spectacular it does go on a bit!)
Take a picnic - you can leave it in the car and walk back to get it (or lug it round if you want). Try and eat lunch either earlier (12 noon or after 2pm) - there will be more picnic tables available as the French are pretty rigid with meal times.
Don't miss the Gladiator show - but don't worry about the queues - you will get a seat so don't feel you have to stand around for an hour to make sure of a place.
Take a pen and make sure you get a timetable for the day's shows (they can change daily) Some shows are on twice so you can decide in what order to do things - a pen helps! Take a camera, suntan lotion and plenty of water. Make sure you take hats for kids - the coliseum can get roasting.
The ice creams, soft drinks etc... are reasonably priced but the meals are a bit overpriced and very uninspiring.
When you arrive you will go through the 19th century France area - this is where the shops are - leave that til the end of the day (the shops have some great toys/souvenirs) which you won't want to lug around all day and you may miss earlier shows if you are shopping.
There are plenty of toilets so don't worry (most are unisex).
If either of your DCs are sensitive (don't like manequins, bangs, gunfire, puppets, cries etc...)maybe avoid the Chemin de la mémoire (DD was terrified and still wouldn't go in again - she's 15!!) It's only a tiny portion of the park and dedicated to the victims of the Wars of the Vendee - but it is a bit scary if you are not prepared for it.
Have a great time - you will really enjoy it. Finally don't bother with the English audio translation - it isn't particuarly good (or accurate) and you can get the gist of the story without the commentary.
Futuroscope - I've never been but DD has been twice (both times school trips when she was 8 and then 10) - it's OK but not as good as PdeF (according to DD) It's expensive for what it is and a lot of the stuff is aimed at adults (older children) rather than kids.
Happy Holidays