Royal Botanic Gardens
A host of attractions here, including the newTreehouse Towers playground. Don't forget the Princess of Wales Conservatory with its carnivorous plants and aquarium. Kew is a huge site, so look out for the hop-on/hop-off Kew Explorer train if small feet are getting tired.
Where Kew, Richmond, Surrey TW9 3AB (020-8332 5655; www.kew.org)