lafergar, you need to explain it to them in a way they will understand, no need to go into the whys and hows, just explain WHAT you have difficulty with now. My DH's health (and mobility) has been steadily declining for years, but your children won't notice the subtle changes unless you tell them. My DH has always taken great pleasure in gardening, but now just half an hour mowing is way too much for him, so we had to adapt, to make it easier to manage, and to find an alternative way of doing things, for example, our grandson does the heavy digging when the ground has compacted, then I do the weeding, then DH can plant new things, or just potter around pruning etc. Our grandson also does the mowing for us, once it was explained to him how it takes days for us to recover from such exertion.