"When the Bough Breaks"...
Under the rules, I can change nothing other than the denouement. But, in a way, that gives the ending much more emotional punch.
The episode goes as indicated until the children dematerialize, with one brief exception: Harry's wooden dolphin is returned to him. Then, instead of what he says, Radue demands that Picard and the others leave at once. Picard repeats his offer to help them, and Radue snarls that he's done enough. After a long pause, Picard orders the Enterprise to beam both away teams back to the ship.
PICARD: "Captain's log, stardate 41 whatever. We have received a text only message from the Aldeans. They want nothing more to do with us, or any other Federation vessel. We have transmitted Dr. Crusher's research, along with a further offer of assistance, and have received no response. It would appear that the vast knowledge that the Aldeans offered to share with us will now die with them.
On a happier note, all of the children are settling back in quite nicely. Their parents have expressed their gratitude, to myself and to the away team. All indications are that they were treated well during their days of captivity. Had they gotten the chance, the Aldeans would undoubtedly have made good parents. Though I know that we could have done nothing else, I find myself strangely sorrowful that the last survivors of this great civilization will soon perish, and their planet will soon revert to legend for the last time."
Data indicates to Picard that the Enterprise is picking up energy readings from the surface. The Aldean shield has been restored, and the fluctuations they previously exploited have been repaired: there's no going back. Picard acknowledges, and tells him to plot a course out of the system at warp 4.
As the Enterprise departs, we cut to Harry and his father's quarters. They are watching out the rear window, and see it as the planet shimmers into invisibility once again, presumably forever. Then, the camera pans in on the shelf, and Harry's dolphin. Fade out, roll credits.