If you do one activity, raft the Ayung — it is the best fun-per-rupiah in Bali and works for nearly all ages. Wear clothes you can throw away mentally; you will be soaked and possibly muddy.
Do Batur only if a 2:30 am alarm does not ruin the next day. The sunrise rewards it, but plan a lazy beach afternoon after. Skip it in the rainy season (roughly November–March) when clouds often eat the view.
Combine ATV + rafting in a combo package if you want one big adventure day — operators usually bundle them with lunch at a discount.
The Bali Swing is for the photo, not the thrill; go if that photo matters to you, skip it if queues for a 60-second ride sound annoying.
Skip canyoning unless everyone swims confidently — it is the one activity here with real technical demands. Round out the trip with water sports at Tanjung Benoa or a snorkelling day; planning basics live in the Bali guide.