Exes hide their casual dating from sonQ: Iím a divorced woman in my early 50s with a 23-year-old son, "Dave," who I am very close to. My ex-husband, "Jim," and I split up about 12 years ago and managed over time to become friends again and co-parent effectively.I have come to see that Jim just isnít cut out for commitment. Heís single again after and I never remarried.A few months ago, I took Jim out to dinner to thank him for throwing some business my way and one thing led to another. Long story short, we have developed a very casual relationship ó for lack of a better term, "friends with benefits."Iíd like to keep this a secret from Dave as I donít want to give him the idea we might be getting back together. The problem is that Jim spends the night about once or twice a week and Dave is in the habit of dropping by my place frequently and always unannounced. We canít go to Jimís place since I have two dogs and a cat that canít be left overnight. Jim also refuses to take a cab or Uber over. He says if Dave finds out, weíll just deal with it then. Should we just keep our fingers crossed that Dave doesnít find out before this thing ends, or should I somehow find a way to tell him upfront?Keeping a Secret From My SonA: Youíre casually dating your ex. OK then. You made the choice, now pick your preferred consequence: letting your son walk in on this news, or telling him yourself.Not that itís mine to make, but the choice seems obvious. "Just so you know, your father stays over here occasionally. I didnít want you to find out by walking in on him one day." When he asks you whatís going on, you say, "Nothing serious, weíre just friends." .The getting-back-together prospect might have meant a lot 12 years ago, but surely now Dave can handle more nuance.And finally: Itíll be weird for him, but only if he doesnít give it more than a momentís thought. You were drawn to each other once, so why not twice?