I am not very experienced with your situation but I would start by stepping up the training, ideally privately with someone who knows the breeds. Aside from training, make sure they are both getting the individual attention, exercise (these are two VERY active breeds),and mental stimulation they require. I wouldn't worry about the dog park for now. I would try to get them to a happier, more confident place, then work on socialization. Good luck, you will get there!