Is the usage of “at play” limited to children’s action?

Time magazine picked up the topic, “Chick-fil-A meets a first amendment buzzsaw” in its 10 most popular stories of this week, which was followed by the following lead copy:

“The issues at play are the personal view of the owner of the restaurant chain and the philanthropic efforts of the private company.”

I understand “the issues at play” here means something like “hot issues” or “issues in motion, or in the process,” but I don’t find the pertinent definitions of “something at play” in dictionaries at hand.

Oxford Online Dictionary defines ‘play’ as a mass noun meaning (1) activity engaged in for enjoyment and recreation, especially by children by showing the example of usage: A child at play may use a stick as an aeroplane. (2) behaviour or speech that is not intended seriously: I flinched, but only in play.

None of Cambridge, Merriam-Webster, and OALD carries “at play” as an idiom.

Ngrams for at play,in play shows high usage of both since before 1840, with the latter significantly surpassing the currency of the former since 1910 until recently.

I assume “at play” is definitely a generic reference not limited to children as Oxford Dictionary defines.

Do you know why this apparently well-used phrase is not included in popular dictionaries other than Oxford Online Dictionary, which shows limited usage?

Solution 1:

In play is the correct term here, as it refers to items that are currently in use in some process (and does not pertain to children in any specific way). "Once your hand is beaten, the cards are thrown out and are no longer in play".

I would also suggest that the issues "at hand" would flow off the tongue even better than "in play". At play, I believe is really pushing the boundaries of what that phrase means.

Solution 2:

As I see it, at play here implies influencing/ controlling.

The issues at play are the factors that affect the decision or drive the outcome.

The word play has far too many different meanings beyond those mentioned by you.

Solution 3:

As noted in etymonline's entry for the noun play, «Meaning "free or unimpeded movement" is from 1650s.» This meaning of play is seen in wiktionary's sense 9 of noun play, "The extent to which a part of a mechanism can move freely", but it also allows issues at play or issues in play to mean issues that are under discussion, with outcomes still to be determined.