New pup in the house

I have a mini-dachshund that is about ten months old.  Then my wife bought me a golden pup for Christmas.  The pup is already bigger than the dachshund, and they wrestle all the time.  My wife and my girls want the dachshund to be allowed on the couch with them.  Is this ok, or does it set up the dogs for a dominance problem?  Also, should we let them wrestle or stop that because the golden will soon be quite large?