First impressions mean everything
The way you introduce a new puppy can make or break a relationship
You're right.... these dogs have been Kings and Queens of their domain
and a new puppy will generally be seen as a rival
Just who is this little thing coming into MY house and taking MY attention away 
Don't force any introductions
Let the older dog come and investigate on its own
when they do let the older dog sniff the puppy's behind and do what it wants
Don't let the puppy maul or chase your older dog
This will be viewed as threatening
The puppy doesn't know proper dog etiquette at this point