I take my dogs to a dog park by our house almost every week now that it's summer. Our park is small so we don't have seprate parks for little or big dogs. They are very timid when there are lots of BIG dogs at the park, but run around and have a blast when there are little dogs. We stick to the hours when the little dogs are at the park.
Sometimes we just go when there aren't any dogs so they can play with each other instead of others. Whenever we walk their they know exactly where they are going. As soon as the park is in sight they will start crying to go.