A General Tonic For Anti-aging And Boosting Power For Elderly (chinese Herbs/ Tcm)?

Hi,
I want to get a tonic for my parents. They’re old now and have some leg and back pain (lower body pain). I know giving a tonic is very specific to the condition of the parson, but it should be something very general that people can take (maybe to tonify kidney channel) which is not very warm or cold (or extreme Yin or Yang). I heard ‘He Shou Wu (Fo-Ti)’ can be taken daily as anti-aging herb. Do you recommend that? for how much dosing?
Many many thanks,
MJ, Netherlands