If you know the keeper why not just ask him for an answer and not some faceless people with a computer ?
If you know the keeper and your dogs are so well behaved, then surely it would not hurt to put your dogs on a lead for a while until you had passed where they need to be on a lead.
Do you think the keeper is being unrerasonable to you personally or is his sign aimed at others as well, who maybe don't have the same skills at dog training as you, those sort of people who will see you walking your dogs off lead and think they can do the same, letting their dogs run riot.