So for local paddling:
You can paddle within the Pippingford Park training area. This is on the ‘Fishponds’. The pin there is next to the launching area. It’s a bit naff, and the access road is terrible.
Weir Wood reservoir is a good option that’s pretty close. This is the launching area I’ve used before. I think you can also launch from the sailing club bit, but not sure. I prefer the other bit as it’s a lot more sheltered if you stay in the little cove.
Ardingly reservoir is another pretty near-by one. Launch from here.
Piddinghoe pond is another, but it’s a bit further away than the other two and doesn’t really offer anything extra in terms of sheltered water paddling. What it can offer though is a potential launch point for a journey! If your with relatively experienced paddlers you can launch from here. You obviously have to time it right with the tide, or you get sucked out to sea I’ve done it before where we paddled into Lewes and got out here and we pre-stationed a minibus with a canoe trailer in the Tesco car park. Worked quite well!
Then there’s Bewl Water. Not personally paddled there but it looks great!
For details on all of those I’d highly recommended reaching out to the current depwatto.sussex. He knows a lot more than I do when it comes to paddling.
For local walking, your spoiled for choice as far as lowland walks go. You can walk directly out of the camp onto the Ashdown Forest. Lovely area, loads of great navigation stuff.
If you want a bit of variety then you’ve got loads of nice day walks along the south downs way a relatively short drive away. Walking from the west of Eastbourne, all around Birling Gap, Alfriston, Firle, Beachy Head etc etc. That area is bloody lovely! Further was along the Way there’s nice areas along Offham, Saddlescombe, Truleigh Hill, Devil’s Dyke etc.
Sadly there’s no mountains though
Climbing wise, you’ve got a fair bit of Southern Sandstone around. It’s the only outdoor climbing we have down here It’s a bit crap, but for beginner groups it can be quite enjoyable only if you can get the good routes.
Bowles rocks has some good intro stuff. If you stay at the end closest to the car park (Woodland Buttress and Hargreaves Buttress) then there’s multiple easy routes close together. It’s super easy rigging as it’s all top access and all bolted properly.
Harrisons rocks is another nice area, but there’s less easy stuff all close together. Advise a good recce on that one! Harrison’s is also nice easy rigging, but does occasionally require a tree!
But, as it’s all sandstone, you have to top out, untie/unclip, throw the rope down, then walk back down to the bottom. You’re not meant to lower off of the climbs. This can be a bit of a faff with beginners. Check out the Sandstone Code and it’ll explain all.
Indoor climbing there are a few options for. For bouldering there’s Chimera in Tunbridge Wells and Boulder Brighton in, well, Brighton! (who’d have guessed!)
For roped climbing I think your best bets would be High Sports Brighton or High Sports Crawley. I’d recommend Brighton over Crawley as it’s a much bigger centre.
There’s also some other smaller private venues that you can book out too, some with abseil towers. Blacklands Farm being an example. You could also look into something like Hindleap Warren too.
Oh, and if you’ve got someone obs course qualified, there’s one of those at Crowborough. There’s also a shotgun range on the camp, but that might be logistically tricky!
As for local attractions to visit, that depends what you’re looking for?