Trip Transportation

I teach a group of students (~20) during the weekends, ages 8-15. I want to take them on a trip (some place in Manhattan, we are based in Brooklyn) during spring break but I don’t know how to transport them.

My question is how does schools arrange school buses for trips and around how much do they cost?

I would appreciate your help or any transportation ideas

I am afraid to use public transportation because I will most likely go alone with them and I don’t want to lose them