RE: Help with training
For now, let them chase. The check cord is really to reinforce "here" or "come". When you want one of them to come toyou, call him & "reel" him in. When he gets to you, give him lots of praise for doing what you wanted him to do.Otherwise, let them drag the cord behind them w/o holding it. Let them run & be puppies for a good while! The best training advice I can give you right now is "SHUT UP!"
As far as them not liking leashes, TOO BAD! You're the boss, not them! They will get accustomed toit as long as you don't give them a choice in the matter. But keep the serious stuff out of the field for now.