I have direct to Omer, but what's the ask?
I would say קבלת עול מלכות שמים as per above followed by singing Ani Mamin.
Would be nice if it's preceeded with a statement/explanation that everything we are doing is a השתדלות בדרך הטבע, but as yidden we know that everything is from Hashem (even if we don't understand it).
I don't know about pre-game. This should be at the point when the crowd is largest!