the dad was being excluded/ignored
You are making an assumption as to this man's feelings. And you can't do that. Just because he was sitting there without a gadget doesn't mean he was feeling excluded, ignored or anything else. He may have had his own gadget and not taken it out just because he wanted to sit there and relax. And maybe even relax without talking. That's not an unreasonable thing to do. As an introvert, I completely understand the need, sometimes, to just.....sit. Not talk. Not do anything. Just relax and decompress. Be quiet and alone with my thoughts in order to recharge my own batteries.
Again, if you don't like people using gadgets at the table, by all means, make that rule for your table. It's perfectly legitimate for you to do that. You have that right. What you don't have, though, is the right to impose that rule onto other tables of which you are not a part. You don't get to require that they put their stuff away any more than they require you to pick one up and use phones or iPads or other things at your table. This is one of those times when you really do have to mind your own business and not get into other people's business. Because other people's tables don't involve you at all.