How are you adventurous with your family on a budget?

[DullardFrigate]

Just that really. I need some ideas of cheap things to do in the UK and away.
We do a lot of walks (or hikes as I think that sounds more adventurous to kids), take bikes to places, go and travel cheaply somewhere.
Any suggestions for particular areas will be welcome.

Camping is a great adventure for kids (at least younger ones - how old are yours?). You do need the gear but after that it's cheap.

Geocaching.