Tŷ Mawr Country Park is one of my favourite days out with young kids becasuse there is so much to do here - a play park, pump track, farm animals, a river walk, cafe, ice-cream and even a longer walk to the Pontcysyllte Aquaduct. (A lovely 40minute walk with a 7year old, on riverside bridleways and forest tracks takes you to the bottom of the Aquaduct - which you can walk up to the top of, but we decided to stay at the bottom for a paddle)
Parking: £1 all day