Advent calendars gone awol

Last year I bought each of my 5 grandchildren a chocolate advent calendar. However, when I went to my daughter's house in mid-December I noticed the three I'd bought for my granddaughters weren't anyway to be found (and the eldest confirmed they'd had no chocolate calendars - I asked in a roundabout way so she didn't realise I'd given them to her mum). My DD obviously decided not to give them to the girls but not told me. I didn't say anything but yesterday I almost bought a few calendars for when I see them this weekend but realised when I got to the till that they would probably also do a disappearing act. I can't give to one set of grandchildren and not the others though? It's just a small chocolate per day - surely that's not an uncalled for treat at this time of the year?