You may want to check out the lounge Sala Formentor on your return flight from PMI (airside, D gates but easily reachable from the C gates). Unfortunately, no view of runways.
There is also a kids' zone in the lounge Sala Formentor at PMI. Not very large. If I remember correctly: Two mini tables and chairs, crayons, a few sheets from coloring books, tower of Hanoi, ...
Very kind lady at the check-in desk. In addition: nicely air-conditioned, calm and relaxing atmosphere.
In case you need an elevator for your kid since the lounge is one level down: If you stand in front of the glass doors, it is a bit hidden, about 5m on your left.
Hope this helps a bit.
Have a safe flight!