So tomrrow i have to go in front of my full schoool...?

and when it is your bday you go up and get a blessing however it is not maditory. i dont want to go but people are tellling me that i have to go. i dont want to go up because my face turns bright red is there anyway that i can tell them NO without sounding like a B*&^$ and when i tell the this my face will probably turn red so what can ui do so my face is not red when i go up or/and how do i tell them no!?!