my 4 year old has a school outing coming up where she will go quite far from school and home. its more like an open trek. i am not very convinced but hubby feels its good to send. what would you suggest moms?

My sister is know in the same situation. More exactly - our mother. I am trying to convince her that my younger sis will be ok and feel good with her classmates, but mom is worrying. What arguments should I bring her for helping sis?