When my daughter plays organized sports instead of accompanying me to shul, I bless her with the following:
May you overtake your foes.
May you run and not grow weary.
This prayer draws from the following sources:
I have pursued mine enemies, and overtaken them...
But they that wait for the Lord shall renew their strength;
They shall mount up with wings as eagles;
They shall run, and not be weary;
They shall walk, and not faint.
When my daughter (now 10) is older, she will know that I was blessing her life, rather than her games.