Holiday tipping

What is the best way to tip the staff in your building? We have a list of 9 names but some of them I never see. I thought of a card addressed to all nine with a bunch of cash and basically leave it up to them to distribute amongst themselves. Or maybe give the card to the super and ask him to distribute to his staff as he says fit. Or just buy a bunch of target gift cards and give them out as we see them? My worry is we would miss a couple. Finally, we have only lived in the building for 5 months. Do you think is appropriate to “prorate” the gift amount based on that or it’s frowned upon? Sorry for all the questions, although we have lived in condos all our life, almost all of them have been smaller, self-managed with no or minimal staff. T