Too expensive of a hang out?

This guy is my good friend. Honestly one of my best friends. Been friends since grades 9-10 (hes a year older than me). Now we are 27-28.

He is in the midst of a divorce. She is spiteful and dragging it out longer than it needs to be. He has the kids full time. He has had them for over a year consistently besides the odd time she takes them during the day. They live with him. He supports them financially on his own. Takes them to and from school, daycare, appointments, swimming lessons. He foots the bills for all the extra stuff too. A lot on his plate.

Next weekend the two kids are hanging with his mom. She wants to take them to her trailer. So for the first time in forever he has three whole days without kids. Trust me when I say this guy needs a break.

So I told him let's do something and he was like sure whatever you wanna do. He's adventurous. Always has been. He's never been jet skiing. So I wanna rent Jetskis for half the day. Its $350 per rental. We would obviously need two. Its not a date. Don't get it twisted. And yeah a guy and a girl can be just friends with no expectations. Do you think thats too much money to drop? I'm not into him romantically. But heck. Sometimes people need to be spoiled. Need a break. A fun outing