Linda,
There is a different answer for each restaurant.
When you go to
'Ohana at the Polynesian Resort you are not entering a theme park, so
NO, you do not need a park ticket to get into the resort or the restaurant. If you are driving you can even park at the resort. Just tell the gate staff you have reservations.
If, however, you are going to
Tusker House at the Animal Kingdom Park,
YES you do need a park ticket. The restaurant is located in the Africa land within the park, so the only way to get there is to enter the park.
I hope that this helps? I am glad to answer any follow-up questions that you may have. Just go to my bio page on the site to ask. By the way, these are both great dining selections, I am sure you will enjoy them both!
Have a magical (and delicious) vacation!