i would help you to ask the other classmates who do no enter the competition to lend you the shoes. please give me your size so i can ask on your behalf.
I ' ll ask those school mates who' re not in the competition to lend you the shoes first. So can you let me know the size of your foot? Thank you so much !
I ' ll , who' re ( = I will, who are ) - use it verbally. In written English, you write " I will, who are ".