The National Trust's 50 Things to do Before you are 11 and 3/4 campaign is a great way to get kids involved in the outdoors and nature. Hannah has her own list here.
I am still working on getting my wife to agree to us turning our back garden into a vegetable plot but in the meantime, we have been growing a few different veggies. Each year, I plant some chilli peppers. This year we also tried peppers. Hannah and I have already had one when it was green and we decided to leave this one to see if it would fully ripen to red. As you can see, it's nearly there:
As well as the peppers, we have grown strawberries and some herbs (Hannah likes to munch on the chives). Not the most productive garden but Hannah's pretty proud of the peppers and I think it qualifies for the list.