Hi Trista,
Thanks for visiting the Moms Panel with your question. Each theme park requires park admission, which is what makes adding the park hopper option to your passes so practical. If you used your park pass at Magic Kingdom that day and then enter Epcot a second park pass will be used, even if you are just going there to visit a restaurant.
If you're mind is set on going to Epcot for dinner after a day at Magic Kingdom, I would suggest that you upgrade your park passes. I don't know when you'll be at the parks, but you can upgrade at Guest Services at your Disney resort or any of the theme parks when you arrive.
There are some fantastic alternatives if you don't want to upgrade or use another park admission. You can stay at
Magic Kingdom and dine at one of its amazing restaurants, or you can find another restaurant located throughout the Disney resorts.
Disney Springs is now open and offers so many tempting dining options. My favorite is
Morimoto Asia..if you go there you HAVE TO try the ribs! There are so many places to choose from; you may end up thrilled that you didn't dine in a park!
Hoping this information helps you. Have a magical vacation!