And here I though Heaven was about God.
True, but Scripture makes it clear that God isn't the only person in Heaven. Angels are there, for instance, and saints. In Heaven, we will be perfectly happy; only God knows what we need to be perfectly happy. Pets on earth serve as a substitute for the love we don't receive from other people, and the love we don't feel we receive from God. Obviously that won't be a problem in Heaven, where we will all be perfected in love, like our Lord.
Ultimately, at the end of time, there will be "new heavens and a new earth," where God will dwell among men. Will there be animals? I don't know, but the fact that God created animals for man at the beginning suggests that they'd be included in the renewal of creation at the end. He must have believed that the animals would be of benefit to man, and it wasn't as food or labor, at least before the Fall.
Of course, it says Revelation 22:15 that dogs will be outside the Heavenly Jerusalem, and that's fine with me. They poop all over the place, and bark when you're trying to sleep, or just walking by on the sidewalk. My cat never went into a frenzy because someone wanted to go to their own mailbox!
No, God is everywhere, even here on earth, so heaven isn't just about God. If heaven were just about God, then Jesus wouldn't have bothered to talk about "many mansions".