I say this with kindness, but at 4.5 it may be more difficult to connect with homeschoolers. Our group doesn't admit families until the oldest child is at least 5 and in Kindergarten.
Do you have a local yahoo group where these other meetings are getting posted? If so, why don't you just pick a day and post it on the group as a park day? Maybe there are other families in your area that feel the same way you do, but they don't have someone to take charge and make it happen.