Did you start them on it early, and now they have lost interest? Or are you trying to generate that interest now, at this age?
For my young kids, we are always doing things outside, except in the heat of the summer. Day hikes, 'hunting' trips (walk around in the woods with a gun, and drink lots of hot chocolate), etc. I try to include things that they think are new, or novel, or most importantly, bear some perception of being 'adult'.
My kids (4 and 5) love to walk around in the wods around our house at night with a coleman lantern. They think the lantern is something special - a privelege granted them for being responsible. Guns are the same. "hunting for them is mostly about drinking hot chocolate when we stop to 'look for deer'.
At an older age, it might be tougher if they haven't developed a love for the outdoors already. Again though try to meld it with something novel or 'adult' something shooting, dirtbiking, ATV's etc...
Not sure I'm much of a help here - just throwing out ideas.