Yes, the question is subjective, but only because all poetry is so it's fine.
Here are my two cents which may or may not disagree with everyone else, all defensible interpretations are valid.
"Teach us delight in simple things,"
Teach us to enjoy the little things in life so that we are always happy
And mirth that has no bitter springs;
and give us the gift of being able to laugh whole-heartedly without interference from the "bitter springs" of grief and trouble that bubble beneath the surface
Forgiveness free of evil done,
and forgive people freely, not bearing grudges
And Love to all men 'neath the sun!
And love everyone on earth. As Alex pointed out, "'neath the sun" is borrowed from Ecclesiastes. It's a motif that appears many times throughout the book. A close reading shows that the phrase refers to the mundane, prosaic, aspects of life that people tend to view as unimportant. I think that this line means "to love everyone and everything because the ordinary is also extraordinary."