I'm also a father to two great teenagers who are with me alternating weeks. I do my best to be that dad who says or does at least one thing a day to make them roll their eyes, even if it's just a dumb joke or giving them a hug in front of their friends. Yeah, *that* dad. I can't help it, they're really awesome kids.
Swimming has been a longtime passion of mine but it's a solitary endeavor. I have to confess that biking on the towpath or hiking in the metroparks (preferably heading towards Fisher's for ice cream) sounds way better with the right person. Hell, I might even try yoga if I'm asked really nicely...but no promises.
As for dating, I think this short essay explains it best. http://markmanson.net/fuck-yes. Good luck in your quest.