(Goblin is nearly 4)The Vyne which is owned by the National Trust. This place is very kid friendly and I would recommend it to anyone who loves outdoor play.
There is a wood at the Vyne but we didn't get a chance to explore because we were sidetracked by the toy tractors, wheelbarrows and bouncy animals that had been left out on the grass by the apple trees. Goblin was in vehicle heaven - to the extent that tearing him away when it was time to go was not a pretty site.
For your nearest National Trust place check out their website http://www.nationaltrust.org.uk/