Is there a trick to help kids know which direction pawns are going? My 5-year-old old daughter very often forgets which direction a pawn is moving. This is confusing especially at endgame studies.

I use a marker pen to draw two eyes on the pawns so that her pawns are facing the enemy and their pawns are looking at her. But this is not applicable online and I am fearful of its side effect when she plays with others on an unmarked board later.

Any suggestions?
At 5 years old a child's brain is still very immature. The good news is that it is also developing very fast. The easiest and most effective solution is just to wait. Within a year or two the problem will have solved itself as your child's brain develops enough to satisfy your expectations.