Replying to Ski lessons

My sisters friend asked me if i could give her two 12 year old daughters a 6 hour private lesson at deer valley and i don't know what i should charge them.

im 17 with no certification or anything

i don't ski at deer valley but with my snowbird season i'm should get a free day pass there so i wouldn't have to worry about paying for a lift ticket

i was thinking of charging about 250$ for the day do you think i'm shooting too high for not having any training myself?