Janeway goes back to get a Dodo... Captain Braxton stands there between she and the last Dodo arms folded with a disapproving scowl on his face.
2 whales are not going to bring back the species.
3 counting the kid.
Now either the Federation council sent back hundreds, perhaps thousands of more missions into the past to harvest more whales of several subspecies... Or they cloned the shit of all the detritus from the museums... Or even cloned all the whales from the past, rather than actually bringing them forward, because what if the whales never died out, but they all just jumped forward?
Point is... Man had the technology to revive any and all extinct species which they had dna for, and chose not to. They must have rules about playing god and dead is dead, because lets face it, if they're bringing back so many, many, many, many animals through cloning, how long until they start bringing back human celebrities as clones?
Hundreds of planets by the end of the 23rd century would have been seeded with cloned Terranian wildlife including whales, surely?