Honestly, they probably won't ever integrate.
I have 4 ducks that I bought last summer, all turned out to be drakes; I then bought 4 ducks to go with them; A friend of mine 'donated' a drake (only duck she had left after her dogs got done); I bought a pair of cayugas; I hatched 2 pekins (one male, one female), I hatched some cayugas and bought some rouens; I traded some chickens for some other rouens. The youngest are the rouens and cayugas, which are about a month younger than the pekins I hatched.
The way they are grouped is like this:
The first 4 are still together, plus one of the ducks I bought to go with them (only duck left from that group);
The cayugas and the drake my friend donated are another group.
The pekins I hatched are another group, and they have adopted 2 younger pekin ducks that we bought. One of the month-younger rouens I bought is with them, cause she is the only one left from the cayuga/rouen group.
I have 2 cayuga ducks that I hatched, and they hang out with the goose they were raised with.
The cayugas I hatched and the rouens I bought (3 total) were all in their own little group until there was only one left.
So they will probably never integrate, but will tolerate each other. Sorry if this looks like a bunch of jumbled mess, but at least I know what I'm saying