We've been to Lake Colorado City state park many times. It is ok, but not really a destination park for us. The lake has been severely low for several years. We stop there for one night only as it is halfway between home and a common destination. The park facilities and people are nice, it's just that the environment is not pretty. Never been to Abilene state park.
Not to far away are Palo Duro State Park or Caprock Canyon state park. Those two parks are in an interesting geological area - lots of hiking- and could occupy someone for three or four days. Of the two, I like Palo Duro better, but both are nice. Maybe three days at each?