Which site(s) are you going to be at? A few urbs, inc me, live in the area.
- Beaches - Barton/Milford are closest I think but Bournemouth's not far - Boscombe is my favourite but it's generally looked down on
- Motor museum @ Beaulieu (though maybe not cheap)
- Loads of walks/cycling (though tbf I don't much like cycling in the forest - too much on the roads and no cycle lanes - though there are a lot of gravel tracks)
- Calshot has got a massive activity centre but again I'm not sure of the cost
- Horseriding
- Kayak/canoe/SUP etc (depending when you're around, you can borrow my kayak if you want)
- Fordingbridge has got a big waterpark where you can wakeboard/waterski on a cable system - my nephew had a party there and loved it - banana boat rides etc
- There's loads of 'experiences' you can do - archery, chucking axes etc
- Depending where you are in the forest, Southampton is close - pretty uninspiring but there's the Titanic Museum, shopping centre, cinemas, chain shops etc etc