Donald Trump Jr. & Estranged Wife Together at Mar-a-Lago After Divorce Filing

Donald Trump Jr. and his estranged wife, Vanessa Trump, might be getting divorced ... but they're clearly spending Spring Break together for the sake of their kids.

DTJ was spotted Sunday at his dad's Florida resort, Mar-a-Lago, with Vanessa and a couple of their 5 children in the pool. You see Vanessa's got her own chair next to her estranged husband's, and even sticks her feet in the water ... looking on as Don plays with the kids.

Eyewitnesses tell us Don and Vanessa showed zero PDA, but they were talking and seemed to be in relatively good moods. He's been posting photos and videos of his kiddos on the golf course enjoying their vacation.

As we reported ... Vanessa filed for divorce a little more than a week ago after nearly 13 years of marriage to the President's son. She's seeking an uncontested proceeding, which signals everything from child custody and property might be hammered out already.

Trump Jr. is said to have had an affair with Aubrey O'Day, who once competed on "The Celebrity Apprentice." We're told she absolutely had a sexual relationship with him during his marriage to Vanessa, but that's not why they're getting divorced.