Many parks have free or cheap activity program, and I just picked two examples: Crowder Park is looking up to the sun, and forward to harnessing solar power on Sunday from 2p-3p. $5 for the entire family.
On the opposite side of Raleigh, Blue Jay Point is focusing on water and all the nice little creatures that live in it. This is on Saturday from 10-11.
Photo is by Rhys Asplundh