My brother is 8 I am 13...?

My brother and I are 5 years apart and when I was little I would go to the mall and see Santa Claus we've been doing this almost every year until this year. I didn't want to see him last year, but after a long fight with my mom had to go. This year she says I don't have to but she wants my bro to go. How do I tell him I'm not going without telling him the truth about "santa", I need help!! If i tell him i just don't want to go, then he'll know that he's not real.