It depends on what their interest are really. For the parents: Gardeners might like a hori hori knife, gloves, kneelers etc. DIYers might light a little bendy magnetic torch or a magnetic wrist strap for screws (also great for holding sewing needles for crafters). Gin sets, glasses botanicals are really popular.
As for your Nan, would she like a bed jacket (my grandmothers both loved them at that age!) or maybe a photo calendar of the family marked with all the birthdays etc.