Doganjo, to try to help you - my ducklings hatched same day as yours. Have been mixing with adults now for just over a week and sleeping in same quarters for last few nights. This is how I did it, don't know your setup but maybe you could adapt it:
Appx one week of:
Night - Ducklings in sep sleeping quaters to others. Day - Ducklings could see out through temp chickenwire fence but not get out, so all could see each other. Fed inside sep to others.
Followed by appx 3 days of:
Night - Ducklings still in sep sleeping quarters. Day - Ducklings out with others (they have lots of room to get away from others if necessary).
Now:
Fulltime with adults. Night in same house but a few sep haybeds made up inside so ducklings can stay together.