Presents for grandchildren going abroad

Try Googling “hugs across the miles”. We were in the same situation as you five years ago and bought a hugs across the miles cushion from Not on the High Street for our granddaughter. Not sure if they do them now but one certainly came up on various websites when I just googled.

Something to make might be good, depending on what they are into and how much you want to spend, dry clay, art, cooking, planting etc.

This way there is something to open and do that will have been used before they go and may result in something they make which will be left at your house.

A special family outing to somewhere they may not have been - then plenty of pics which can live in "the cloud"?
Too young for the Harry Potter Studio Tour perhaps (or perhaps not) but I took 2 Ds and 4 GC on Monday and they absolutely LOVED it.
Memories take up no space in one's luggage!