We are here right now! Going home tomorrow. :( Had tickets with our hotel, full week, we've been every single day. My kids (13, eight) love it.
Bring water shoes, invest in good ones. We bought the cheap (€10 a pair) ones here at the park, they served their purpose but are in the bin now. Our feet are killing us. The soles are very thin and the insoles become unglued and even more uncomfortable. I'd recommend buying better before you come, but if you don't manage to, the ones onsite are ok. Toilet floors were disgusting, do not enter without footwear.
Definitely do the fast pass if you can. We got the €28 ones, one ride ticked off in a four hour slot. Can whizz round in about 2 and a half hours, ish. otherwise you won't do every ride in a day.
It's a lot of walking.
Food is not great for us (vegan), but probably ok for everyone else. I've brought snacks in and not been searched.
It is very very busy. The lazy river is rammed, and so busy you don't always get to go down the left lane (to the slide). Big wave pool also rammed. Got a bit hurt by all the bodies. I wish they'd limit the number of people allowed.
Have not enjoyed seeing the sad sea lions.
Lockers dinged our first two days, the queues were horrendous. We then bought a waterproof phone case, and didn't bother with lockers again. Took nothing worth stealing, and left our small bag at the bottom of each ride.
You can't take your phone case on the tower of power though. Weird trust system of handing it in up there, then going back for it. So I heard. I didn't actually go as my 8yo isn't tall enough for it.
Free bus has been generally good, but not always guaranteed you'll get on. Factor in occasionally needing a taxi.
Overall, would definitely recommend. My two have had a brilliant holiday. I need a holiday to recover from all the walking.