If you buy tickets (UPH) at the time of check in, there is no problem. Each person's ticket/pass can be sold seperately. Each can buy whichever type of pass they desire. For example, one could have the AP, one could buy a UPH, and the last might only want to go one day and could buy a one day/one park. It is all your choice.
I believe that if you order the passes ahead of time from CRO or WDTC that you have to purchase the same thing for everyone. But at check in you can make your own decisions on purchases.
Bianca