Tell him that the dinosaurs were taken on the Ark like all the other animals.
So you are just going to say fuck it! and lie to the kid? That's some real stand up parenting. Complicated questions? Fuck it, just lie to them.
Noah probably took young/baby ones. :-)
You say that as if it would somehow make the story true. Just how fucking deluded can you possibly be?
Plus, the average size of dinosaurs was roughly that of a sheep. They weren't all huge!
Uh-huh, you are right. But, if Noah only took the teenieist, tiniest little bittiest of each species of dinosaur then guess what? THEY STILL WOULD NOT ALL FIT ON THE FUCKING BOAT!!! Do you have even the slightest comprehesion of the millions upon millions of different animals that would have to be on what amounts to little more than a poorly built raft?
Even if you retreat to your little "Well Noah only 'Kinds' of animals" argument, which is total bullshit because you can't even say for certain just exactly what a "kind" is, You still wouldn't be able to fit them all because dinosaurs are not a single species, "kind", or anything closley resembling those things. Dinosaur is a word used today to describe thousands, if not tens of thousands, of tangently related creatures.
But hey, fuck it. When your kids ask you questions about reality that don't square with your fairy tales then just lie about, that'll educate them real good.