I've always opted for one site with sub directories as long as there was not an overwhelming need/reason to create separate sites or sub domains. I believe in the theory that creating one website and adding pages to it will help create an authoritative, large and resourceful site. You can SEO one website and pass juice around the site. With multiple sites or sub domains, the need exists for separate SEO for each and every site/sub domain. If you have the resources available then great. If it all falls into your lap, it may be a monumental task.
I am not quite sure how I would handle your situation though. I like realityhacks idea of creating a home page with three large, sections highlighting the features of each group with a bold call to action which will lead you to more information. I agree with all that he noted about this thought. You need to identify what the difference and need is to separate the 3 target groups before you decide to create separate sites for them. If the info is the same for all 3 groups, I think a site about the different adventures with packages broken down per group would be my choice.
"Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime." Chinese Proverb