Hello Ethan I agree that to say "a win-win situation" would be better; but I would like to suggest that you say something like: "This program will benefit all our student groups" "This program is beneficial to multiple groups of students" or "This program will be beneficial to a multitude of student groups" I hope that helps!

Informally you can say, "It's a win-win for all groups" (even though there are more than 2 groups), but better to reword it the way Lyn suggests.

the "win-win" is an adjective to modify any nouns , for example, a win-win opportunity, a win-win situation , regardless of how many parties are involved , so yours as the "a win-win program" is only correct form to express what you want to say. I am chinese , perhaps knowing you want to express the "三赢程序，也许涉及到一共三方(我方，对方，和 其它方?)，而不是 "双赢程序"(只涉及两方，我方和对方)， (也可能不是这个意思)。Unfortunately ,it is incorrect to write the " win-win-win program ( or triple win program) , if you want to clearly express such meaning as what I denote in chinese , you'd better tell me what three aspects your program refers to , which your program will let get benefits. If possible, directly here tell me in chinese…,.if the three aspects are A, B, and C , your wanting possible correctness is: the win-win program for A, B, and C. By the way, triple win is not correct in the context of your expression , triple is an adjective ,meaning three times( 三倍的) or having three parts(由三部分组成的), … maybe , you don't know how to exactly express what is you real meaning in English, don't worry about this, you can write here in chinese to tell me the details.and I would be glad to offer a help to translate it into English.

Thank you very much for your detailed information. I learn a lot from you and really appreciate it.

In that case I would go for: [School name] International Summer Camp: Benefiting Foreigners, Taiwanese Students and Local Residents.