We have a set from the Macro , a few years ago now.Take note on what channel you use as we found we were accidently having conversations with other kids who then called me mom.So set some rules nick names are good, and if you have to change a channel go up to a certain one your kids know of.
I find even if I can't get a signal to call on a mobile then it's normally possible to get a text through. And then again, how big are the campsites you go to?!? I can normally summon my kids from the far flung corners of the fields with my big gob!!
We were in Germany 2 years ago travelling with friends who also have a motorhome. They had lent us a two-way radio, and we found it a great help in keeping contact with each other whilst driving. Wwe are thinking tobuy our own from Lidl.