"Night at the Museum 3" closes out director Shawn Levy's effects-driven, family-friendly trilogy with three separate farewells. The most bittersweet parting involves the late Robin Williams. It's both touching and difficult to see Williams, looking game but wan, portray Teddy Roosevelt one last time, as Teddy and his fellow Museum of Natural History dwellers (from Attila the Hun to the T-Rex nicknamed Rexy) travel to London's British Museum in order to give the movie somewhere to go, something to do, new institutions to disrupt.

Mickey Rooney constitutes another farewell (he died in April; Williams committed suicide in August). He turns up, briefly, as one of the devious night watchmen from the first picture, now in a retirement home with his cohorts played by Dick Van Dyke and Bill Cobbs.

In the new movie there's a pretty good relationship at the core, that of single dad Larry and his restless teenager now played, appealingly, by Skyler Gisondo. Father/son issues abound in the script by David Guion and Michael Handelman. Fruitfully, "Night at the Museum 3" introduces a new Neanderthal named Laaa, played by Stiller. The caveman recognizes in Larry a distant but undeniable blood relative — the dad (or, really, great-great-great-great-great-grandson) he never knew he was missing.

Owen Wilson and Steve Coogan are back as the wee cowboy Jedediah and Roman warrior Octavius, respectively; Mizuo Peck returns as Sacajawea, as always distressingly light on narrative purpose. In the British Museum section of the story the most conspicuous newcomers are Sir Lancelot (Dan Stevens of "Downton Abbey," amusingly narcissistic) and Rebel Wilson as a randy night guard who takes a shine to Laaa.

It's a hectic pileup, this movie, but at least in its final laps it takes the time to say its goodbyes more or less properly.

"Night at the Museum: Secret of the Tomb" - 2 1/2 stars

MPAA rating: PG (for mild action, some rude humor and brief language)

Running time: 1:37