I'm all for making friends of multiple people of the opposite sex, it keeps things from getting serious too soon and keep them in perspective.In the old days it was considered proper to date only one person at a time. But oh my, times have changed.
But i think its important to define what is dating. Nothing wrong with spending time with someone to get to know them as a friend. But it should be clearly stated that it's not a date, and both persons are free to spend time with others. And no one should get jealous or clingy.
Just don't touch, as in affectionate touch.
For me that is choosing one of them at which point you need to let your other friends know you made a choice.