Surprised no one has mentioned sports equipment/outdoor toys? That was a common gift for us growing up (usually from my parents though).
I'm not too well informed about traditional sports (balls, gloves, cleats, uhhh???)
Hiking/camping gear: good daypack, sleeping bag, headlamp/cool flashlight, ice cream ball, travel games?
Pool/water toys: noodles, inflatables/floaties, boogie board, inflatable boat/kayak, splashing/spraying devices, games
Other: roller blades/skates, ice skates, bocce ball/croquet (surprisingly fun in spite of its stuffy reputation!)
For activities, consider taking them rock climbing (as young as 3-4 yo), skating, trampolining (apparently very unsafe for <7yo though!), rafting (prob >10-12yo, w/swimming skills), kayaking/canoeing... Some of these are expensive to do regularly but IMO good life experiences and active/exciting/memorable! (I actually kind of hate rock climbing 'cause my family went ALL THE TIME but for a lot of people/kids it's novel and they get excited by it.)