Brought 3 young kids and the oldest at 8yrs old got bored after about 3hrs here. So I'd say break it up if you can. Not that many rides that will challange older kids but it's nice to walk around and marvel at the architecture. It's really hot so bring a hat or umbrella.
Pretty crowded and I went on a weekday! Lots of schools bringing their students there for an outing so you might have to wait quite a while for the popular rides.
Food and drink prices inside are pretty high considering that you can get much cheaper right outside the gates. Just get a stamp on your hand for a return visit and head out to eat and buy drinks.