I think you can still have fun, a long time since mine were toddlers but we always travelled, obviously covid makes that difficult now but plenty can do in UK.
Things I have done since kids were toddlers that were fun
Holidays, always at least 2 weeks in summer, done watermarks, canoeing, gorging, wildlife spotting, rainforest treks, snorkelling in Great Barrier Reef and with seals in Devon, beach, swimming, horseriding, going down waterslide in jungle, ziplining with monkeys in trees, seeing brown bears in wild, skiing, staying in treehouse with loads of wild animals around, staying with lady that looked after injured tree kangaroos and having one jump on me. When kids were little we did AI so all on site and we got a break.
Also tried aquaparks in UK with kids, steam trains, teaching DS to swim was fun as he insisted on being Woofie the dog and I had to be Woofette, parks, days out at safari parks, wake boarding, went to David Lloyd for a while and did swimming and spa a lot, baking cakes with kids, playdates were adults stay and chat, this summer doing helicopter ride, small plane, swimming with seals, alpaca trekking, tropical gardens, spa, swimming, also hired boat recently.