If you want to enjoy
It all starts to go wrong when Sid the ground sloth stumbles across some enormous eggs. Feeling left out by the fact that the mammoths Manny and Ellie are expecting a baby and are about to start a new family, Sid appoints himself the mother of the eggs. (Diego, the saber-toothed cat, is having his own worries about losing his predatory edge.) These soon hatch into baby dinosaurs, but the well-intentioned Sid has no idea how to properly care for them. Needless to say the real mother of the babies is none too happy when they go missing, and being that she is a rather large Tyrannosaurus, that is bad news for the mammals. In gathering up her young ones she picks up Sid, too, and his friends set off to rescue him.
The mammals quickly find that they are out of their depth, but they get some help from a crazed survivalist weasel named Buck. Buck has only one eye due to a past encounter with a large, whitish menace he calls "Rudy." From that point on the film settles into its search-and-rescue theme, even as Sid somehow becomes accepted by the Tyrannosaurus mother. The visuals are spectacular and the direction is great, but the dinosaurs are sometimes annoyingly over-stylized. While most of the creatures in the film are embellished in one way or another, the dinosaur designs are a bit over the top (such as small, Monolophosaurus-like predators that have quills that shiver when the dinosaurs roar).
There are even some dinosaurs that never existed. When "Rudy" finally appeared on the screen, for example, my wife leaned over and asked, "what kind of dinosaur is that?" "It's a nothing-o-saurus," I replied, as the monster was more of a bipedal crocodile than a dinosaur. "Rudy" is a scary villain, especially in 3D, but with so many giant predatory dinosaurs now known I would have liked to have seen an attempt at one like Giganotosaurus.
If you liked the previous two Ice Age films then you will probably like the third one. It is a "safe" movie that is not especially exciting but still is funny enough to be enjoyable (unlike this summer's other dino film). And if you are offended at dinosaur running around with Pleistocene mammals, just remember it could be worse: humans could be riding them.