Michy- I have always found that multiple dogs do better than singles. They learn to play, and try as I might- I can not play like a dog would. Introductions are critical, but I can help you with that. Also the few days, take things slow.
Dogs are companion animals and pack animals too. IMO multiple dogs live longer, happier, and not to mention- more entertaining for us.. lol. I have found the new comer learns from the " other ones." To me its actually faster to train a dog with another dog in the house that knows the rules as dogs follow suit.