IME, it's like everything else with kids: it's the outdoors, but not as you know it! So my DH has had to reign in his tendancy to go for SAS style 30 mile yomps with several Munros thrown in for good measure - much to my relief .
But we have managed quite a lot of outdoorsy stuff, largely carrying DS. For example:
Skiing (DS 9 weeks) involves finding resorts with nice cafes by ski lifts where one person can chill out while other skis up and down.
Walking: Ireland (DS 9 months), Thetford forest (DS 11 months), lots locally (East Anglia) + Peak District and California (DS 18 months). All achieved with aid of very basic backpack and large kit on back of other family member. Day trips only: I hate camping. The one time we did try it, however, DS (then around 14 months) absolutely loved it, and we're going to have another bash this weekend on the South Downs.
Also done a bit of skiing (DS 26 months) with DS in backpack. Greens and blues only, mostly with DH (who is very strong skiier). Still collected filthy looks from conservative German skiiers, though
Now reaching a bit of watershed, as DS tall and heavy for backpack and rather too lazy to walk (maybe all that carrying!). So plans for next few years include extensive use of bikes (DS spends lots of time in bike anyway) on appropriate trails, and quite possibly (although this might seem a bit OTT) pony hire, relying on the pony to carry plenty of kit as well as DS, so we can do longer walks that require several days.
Never done any watery activity, though, (bar punting) - I am slightly jittery about combinations of a bored DS and small boats.