Hi, Gini,
Congratulations on your rescue! He's lucky to have found you!
I had the same concerns when I introduced my tricolor pup, Josie, to my male Blenheim, Jasper, who was a year old at the time we got her. Jasper is a very placid, gentle, almost shy dog, and Josie is his exact opposite. We knew that when we got her but chose her because we hoped she'd bring Jasper out of his shell a little bit. She's done just that.
The breeder told us that it was very important to introduce the two dogs in a neutral location. I had my sister pick Jasper up from my house (we weren't there) and take him to her house, and we brought Josie over there so they could meet in an unfamiliar territory. My sister has a Shih tzu and an Aussiedoodle, too, so there were other dogs there in the mix. Much to my surprise, they both ignored my sister's dogs but immediately came over and sniffed each other. I really think they recognized that the other was another Cavalier! We let them get to know each other and start playing for about half an hour before we brought them home. I don't know how we got this lucky, but Jasper accepted her right off the bat. I wouldn't say they fully bonded for another couple of weeks, though.
We were careful to pay special attention to Jasper and praise him for being with Josie, and we didn't interfere when he'd try to correct her (he didn't like her eating his ears and promptly put her in her place). If I were you, I'd let Bailey know he's still top dog and praise him when he interacts well with Charlie. He may need some time to adjust. I've read on this board that sometimes dogs need a week or two before they accept a new member of the family. You may need to separate them for awhile.
Don't get discouraged, and I really think things will work out just fine. I think Bailey's going to love having Charlie around once he gets used to the idea.
Lori