As with most things in lfe, "your mileage may vary". No one can predict how another person's dogs will react to a situation - hell, not even the dog owner can predict how a dog will react in different situations, especially when there are 3 dogs involved! I think my best bet is to, as suggested, free range the dogs and chickens separately.... dogs all day, chicks for an hour or two closer to dark.
I was pleasantly surprised at the response we got last night when I tried letting the chicks out for the first time. After they got comfortable walking around I asked my husband to bring the boxer/rottie out on a short leash. I thought she would be barking and pulling frantically but instead she calmly observed from a distance. When he came closer, she again stayed calm, but when one of the chicks made a sudden flapping movement, of course the dog lunged for her. It's their instinct - they are dogs! And that was with the other two contained in the house so they couldn't even observe what was going on outside. There is no way I think I could ever be comfortable with 3 dogs free ranging with chickens since they feed off each other and all it takes is for one dog to misinterpret a move by another animal.
Perhaps in a few years when my dogs are old and lazy seniors this could change, but I appreciate the advice and will probably always keep the free-ranging separate. Or who knows.... maybe at some point I can let one dog at a time "mingle" with the chicks, but 3 at a time is asking for trouble, especially since there's only 1 of me to try and get the situation under control. Once it escalated, there would be inevitable injuries/deaths.
Thanks gang..... I will enjoy my "pets" separately. There's enough space and enough hours in the day for all of them.

Sue