I had to do this a number of years ago. I sent each number a text message in advance. Inevitably some never picked up but most did in the end. If all else fails, you can always ask them if their refrigerator is running.

Man, I did some calling during covid in 2020.  But my school at the time sent me home at noon and I had to call a few kids in the afternoon.  Good trade off as far as I was concerned,  But then my Friday school had me start calling every single kid I taught on Fridays and talk for a couple of minutes asking basic questions to.  That was irritating but it didn't really go on for too long in the spring of 2020.  I was fortunately at mostly smaller elementary schools where kids mostly came in from June 2020 and beyond.  Some larger schools had only some kids come in and some stay home.  Middle schools even worse.  For friend who taught there and had to do online classes and more call outs for most of 2020 and even into 2021.  I think it really burned them out.  So glad I could mostly avoid it. 

My main school has always wanted camps even during the height of covid while all my others have cancelled them ever since.  I read the kids "books" or "story" ppts for elementary and add some game or activity then tell my co teacher to find a craft or something to add to it based on the theme.  Problem solved.  (I pull the boss card.  Mwa ha ha ha.)  I have a 3 day one at the end of the month just as schools end. 

Then August, it's off to a beach location like Pohang or Busan or if too expensive, or it's off to Seoul instead.  Motels and hotels along the coast getting booked up and too expensive like crazy.  So, probably off to Seoul.  Plenty of deals.  We shall see. 

Then August, it's off to a beach location like Pohang or Busan or if too expensive, or it's off to Seoul instead.  Motels and hotels along the coast getting booked up and too expensive like crazy.  So, probably off to Seoul.  Plenty of deals.  We shall see. 

      Some unasked for advice: don't go to either Pohang or Busan. Go to the smaller cities and towns along the coast! The beaches are just as good, and they're a lot less likely to be crowded.
Also, motels and hotels kind of suck. One should be looking into pensions, or AirbnBs. If you go with a friend or 2, they're more or less the same price, but you get an entire home to yourself. Last winter vacation, we ended up near Gangneun, rented a pension 5 with a big yard, a deck, and a hot-tub. As there were 4 and half of us splitting the bill, per person it ended up being about the same as a cheap motel. And there's *loads* of stuff to do if you have a vehicle and enjoy a bit of exploring!