She's quite entertained by Mickey Mouse Clubhouse and Sofia, so I'll put a couple of episodes of that on the iPad and she'll watch those.
Depending on what time we're in a restaurant, she'll sit in a high chair at the table, and eat and play with toys etc. But we're going with a group of family and friends and we like to eat out and have some drinks and take our time, so once she's totally finished eating, I'll put her in the buggy, put the iPad on, give her her milk and she'll hopefully fall asleep without us having to leave and without screaming the place down. If we were at home it would be different, but it's as much about not ruining others nights out as it is of not ruining our own.
If we're in a long queue and she's unhappy, I'll probably use it. But there are a few of us and it's more acceptable to make noise in a queue (and in most you can't take buggies) so perhaps not.
I don't need to take her anywhere about her unhappiness. It began as reflux, and then was a milk allergy, and is now a dairy intolerance and she is just very fractious. (I've started several threads about her in times of desperation).
Basically, if I think we / she will benefit from sitting in there and falling asleep to a DVD, I'll use it.
(Of course, Saturdays 20 minutes may well have been a fluke and she might rebel... And of course we'll cope.)