We have 5 little babies and there are no problems whatsoever. They all get along very well but when we got Mylo (he is a puppy 7 months old now) Mikki our youngest and smallest girl (and actually his cousin) was a bit grumpy with him but now they are attached by the hip and where is one you can be sure to find the other one right behind... LOL... Mylo is our second boy and Maxie, the oldest with 8 y.o., is like a father or uncle to him. Now that he gets older he shows him his place once in a while but nothing serious. When it comes to the potty training I found that it helps if there are already trained dogs there b/c it's just natural to go outside and do your thing. The barking is catching though and Mylo is a fast learner...
All together I would say as long as you can maintain to stay the pack leader there is nothing to worry about. Oh... and when it comes to morning kisses there is nothing better than a 5 monster kissing attack to wake you up!