Visiting Versailles can be a GIANT pain. Unless the teens are clamoring to see the palace and gardens, I'd skip it. Long lines to get in, even with a timed ticket---hugely crowded interior tour, with many people who are comfortable with a MUCH smaller personal space radius than I, and a general lack of signage, passive interpretative info, etc makes for a chaotic experience in the palace. I loved walking through the Hall of Mirrors, but the rest of the palace rooms do not stick in my memory. I do recall being awed by the gilded gates, perhaps because we spent so long looking at them while in the endless security line. The gardens were impressive, and I'm glad we visited bc it was a place that loomed large in my imagination through various cultural references. But I wouldn't repeat the experience unless it was just to visit the gardens during a sound/light or fountain show.
NB, buy your return train ticket before you leave the station. We didn't, and ended up in a giant crush of people all trying to use a couple of ticket machines which were s-l-o-w-w. The largely international crowd struggled to use the machines, and no one was kind enough to buy a big stack of tickets out of the machine and sell them in cash to the ppl behind them in line. We missed two trains while waiting, and the lone human manning the station finally gave up and opened the gates and let everyone onto the final train of the afternoon. So we boarded, ticketless, and rode back to Paris. EXCEPT--you have to scan your ticket to EXIT the train station. And we were stuck behind a thicket of law-abiding international ppl, mostly Brits, who were just milling around. We climbed over the turnstiles like good American scofflaws. For all I know, the Brits are still queued up, waiting for a station attendant to let them out. Ha.
Honestly, I'd go elsewhere with teens on the last day in Paris. Use it as a day to tick off experiences they might have missed: shopping or just looking at Galeries Lafayette or the Grand Epicerie if they're into food, or whatever slice of Paris intersects with their interests and enthusiasms. If creative, they might be interested in someplace like 59 Rivoli (former art squat turned studio/gallery) or relish a visit to the Sennelier store on the Quai Voltaire (where artists from Cezanne to David Hockney have shopped).
