Joshua Field Trip to San Francisco

I am asking for money to help pay for my son's field trip to San Francisco with the gifted program. He is nine years old. I thought about telling him no we can not really afford it but I am going to turn to hear and see what happens. I could probably afford to send him by himself with another parent. I just can not see sending my nine year old accross the country without me. So I am trying to raise money for him, his little sister, and me to go.