I would definitely, absolutely, without a shadow of a doubt...NOT see Land Before Time in 3D!
Like I said in a previous topic, 3D does not make a movie better. It doesn't add anything to the movie going experience. "Ohh, it looks like stuff is flying at me, it's so amazing!!!!1111". What I find interesting is that most people today don't even know that 3D has actually been around since the 50's. Except back then, 3D was usually only used for comics. It wasn't until, I think about the 70's when they started using it in movies. And even then it didn't last too long.
Now as for LBT getting the 3D treatment...why? I don't think LBT needs 3D. It got where it is by being a generally good movie. Unless the 3D adds more depth to the story and characters, then it's not necessary. Not to mention that it wasn't even filmed in 3D so converting it to 3D would make for a total disaster. Just take a look at all the movies being released that were originally intended to be 2D only but were then converted into 3D.
So no I don't think Land Before Time needs the 3D "treatment". It's good enough as is.