Lots of walking maps available online:
Taunton and Deane - Circular Walks
Walking in Somerset
Circular Canal Walk, Creech St Michael
Somerset Space Walk
Hestercombe Gardens - £7.90 for adult + 2 children
English Willow Baskets - has a Free visitor centre. Located near Stoke St. Gregory.
There is a place called The Fire Museum, details are lacking through, so no info regarding cost or what they actually have there. Could be worth a phone call.
Rural Life Museum, Glastonbury - entry appears to be Free.
Taunton YMCA - may have sports events for children during half term, low cost. Contact them to see what activities are on this coming week.
The Fun Farm - admission around £13 at the look of it.
Walking in Somerset0 - cost around £5.
Walking in Somerset1 - cost around £28 for 1 Day Rover ticket.