My parents are pretty much in the same boat, serious medical issue and shielding all year and father due surgery in early new year.
I am getting them a flower subscription with flowers arriving once a month starting just before Christmas.
They live a long way from us and we usually have them here for Christmas but won't this year as it's too risky. we hope to see them before Christmas and I will make them up a stocking each to leave on their fireplace and they can open them on Christmas morning.
I'll put mini christmas puddings in each and a mini christmas cake.
Handcream, scented candle, nice soap, fancy chocolates, a magazine and perhaps something else small in my mothers
toblerone, magazines, large bar chocolate, garden bulbs, book of crosswords, and a new mug in my dads
I think they'll be happy with that. I had contemplated getting them a voucher for the garden centre but then i realised that they really wouldn't be able to browse etc due the shielding so thought the flowers would be a better option.
They're v hard to buy for as they don't drink, have no hobbies, don't do much and aren't interested in many things other than strictly come dancing and other tv programmes like that.
We've bought them tech in the past - laptop, tablet, kindle over various years and not one single thing got used ever so have given up on that side of things.