I have had a quick skim of other responses but did not read in detail though I saw the contradiction.
I have kept and bred angels for a long time and under normal cercuimstances I would say don't mix young and old angles together because they will get beaten up. I suspect your large angels are at or close to breeding age which makes them very territorial and aggressive.
Having said that, it does not mean it can't be done. If like you say the tank is big enough (and should have hiding places) then if you get a few small ones they will be ok after a while. However that also depends on the temperment of the male in particular. Once they establish them selfs in the tank, the little ones will get bold and defend them selfs.