Hi Heidi,
Thank you so much for visiting the Disney Parks Moms Panel with your question. My daughter also collects pressed pennies! We have many of the folders designed to specifically hold these pennies. Pressed pennied are a great, low-cost souvenir, and are a wonderful way to remember many of the places that you have been around
Walt Disney World.
For the most part, I believe that you should be fine parking at the resorts to collect pressed pennies. Simply let the cast member at the parking booth at the entrance to the resort know why you are there. Most of the time, I imagine that it will not be a problem for you to park to do so. There are some circumstances where this would not be possible - for example, during the Epcot International Food and Wine Festival, Disney's Beach Club Resort, Disney's Yacht Club Resort, and Disney's BoardWalk Inn are very strict about allowing only guests of the resort or who have dining reservations park in their lots. For a time of year when there is not a special festival, I would imagine that you will be able to park in most resort parking lots with no charge and no problem.
I hope that these thoughts are helpful for you, Heidi. Have a wonderful time planning your magical vacation, and please do let us know if you have any further questions.