The coaches were just tired.
I have to admit: I hate hearing this excuse.
If you are supervising children in a public place, then you need to supervise the children. It doesn't matter how tired you are, and it doesn't matter how high-energy the children are. If you bring children into a public place, they're your responsibility.
I was thinking the same thing.
Sometimes all it takes is a statement of your expectations IN ADVANCE.
"Look kids. We're so pleased with how hard you're trying and you're doing a great job, so we've decided to take you out for ice cream. Here is how it is going to go.
We will walk in together.
We will line up. Coach A will be at the beginning of the line and I (Coach B) will be at the end.
Each person makes their ice cream choice quickly and orders, then the next person in line.
As soon as you have ordered you will go over *there* to wait for your ice cream.
As soon as you have your ice cream you go sit down and stay there.
When everyone has finished we will go out to the cars together as a group.
Whether or not we ever do this again will depend on how well you are able to follow these rules today."
Usually the results are pretty good if the children know with certainty what is expected of them and that there will be future consequences if the are unable/unwilling to comply.
LOL, I had forgotten how much I did this when I was teaching and then again as a mother of young children.