Boy, I'm stepping into the fire here I know but, goodness Brother.............I don't think we should go so far as to believe creatures are mentally, spiritually aware of God. Who He is, and what He is. Just saying........I've known a bunch of critters too, and have yet to see one "repent" and accept Jesus Christ as their Lord and Savior, and be obedient to His commandments. I have never seen any critters "witnessing" to bring other critters into the "fold."
Now, none of this has to do with weather or not there will be critters in heaven, rather it has to do with not making them "human." Human beings are triune creations. Critters are not..........and that is the real difference.
If we accept that our beloved pets will be in heaven and we will know them and they will know us...........goodness, it's gonna be a mess in my Mansion, 'cause I've had MORE than one pet............and I can think of a couple right off that WILL NOT get along with the others.
And what about the guy who just loved his pet spider? Or the guy who loved his pet snake? Then there is the weird kid down the street that had that fire ant farm in his bedroom...........