My son and his family are staying there can we buy 4 other passes to bring are other grandchildren there for the day?

You can get more passes, they will add an extra fee.

We where there and we were able to buy additional passes but we only needed 2

I was just there a few days ago and no u are not able to buy extra passes. U get 6 with your room no extras. Says so on their website.

No day passes

You have to have a reservation to access everything there now.

No, they do not sell day passes. Only overnight guests of the resort have access to the water park.