Yeah cardnials are great little fish, I have tons of pictures of mine doing silly things, and of course when they had babies.
And I really hate to say I told you so. But he's right that those little cardinals may eventually become snacks, if anything they may get more reclusive as they hide from the bigger fish. Putting them in their own tank is a great idea, you may even get a spawn or two.
I once saw a half filled 200 square gallon tank that had only bangaiis and mangroves, really nice tank. Actually, any cardinal is a good choice, you can even get some big enough to keep in groups of 3+ in this tank.
And keep an eye on them, if you're right and they are only 1-2 inches they are not fully grown and therfore don't care about gender/mating yet, once they grow up they might fight so be careful, the only way to know for sure (and even then they could fight) is if you've seen one hold eggs for the other.