aaggressuve behavour between my rescued papillon//chihuahua

Question
I brought my little dog to meet and get acquainted with my son's female and very mellow and loving 80lb. mixed breed yesterday. To my horror my little 7 pounder was agressive and even bit the larger dog's snout. as soon as I tried putting him down on the floor, he instantly became aggressive by barking and growling. When I held him and petted her, he was ok. What do I do to help them get along as I want us all to be together for Christmas????

Answer
What is a good trick is to bring our dog over to your son's house(not the other way around)and put a muzzle on your dog(and the other one if you feel better)that way she can get used to him,and a lot of times once they become in charge(and since she will be muzzled)she can do this without hurting the other dog