There are lots of kid friendly hikes. In fact, there is a very good book about them. I have this book
and have taken my kids on lots of the hikes they suggest.
The recipe that worked for my kids is this: bring lots of drinks and snacks (including food they normally cannot have in great quantities but now can, such as chocolate), have good company of friends, set a clear goal that they understand, follow a stream or go to a lake, avoid bug season or hot humid days, keep away from long steep hills, etc. Views are definitively a plus, if they can handle going up some. Rock scrambling is great, if kids are old enough.
Then there is this guide
for all kinds of kid friendly outings.