A BAD owner doesn't ask and things get worse. When I think of all the utterly basic things I had to learn… really, the fact you ASK shows you are, in fact, a good owner. These are not easy dogs. People fear Rottweilers... trust me, their desire to please make any well bred one nearly push button training. I have had, trained, done rescue and rehab for nearly 30 yrs, and these freaking dogs challenge me daily. It ain't just you, iow.
I have to say, I am not a dog park fan. I like the parks that let you sign out an enclosed area for you and your friends. A park where you are at risk of any nutjob owner/dog, not so much. But particularly with your guys. I hope you find a way to retrain the perfect recall, and to get them back. But right now, you are putting them in danger.
I like this link a lot,
http://www.clickerlessons.com/recall.htm
But once someone posted on not just recall, but creating neuropathways more stable while teaching it.
TRAINING TO COME AND CONDITIONED RESPONSE
From: PCF Click
Do this exercise three times daily for two weeks:
Walk toward your dog until he sits; blow the whistle while within one second
popping a real treat into his mouth. Do this three times for each exercise.
After two weeks, walk across the room and blow the whistle. The dog will
come and sit in front of you. Give him a very big handful of goodies (
REAL treats, not dog cookies). After ten out of ten successful repetitions
of this game, blow the whistle at various times throughout the day from
another room. When the dog comes and sits in front of you, reward.
Take this outside and do "round robin whistle' with the whole family.
Now you have a conditioned response.