Hello,
I have agility dog's the best way for you to get started is to go online to the Kennel club web site on there follow the links to find a club in your area then make contact with them they will be able to help you from there.

As long as your dogs are fit and well there is no age limit on how old your dog can be i retrained my lab to agility at 11yrs old and he loves it they have oap classes at shows the poles are low and no high impact equipment so he loves it the only age limit is on puppies they cannot be entered in to any show's untill 18 months old and cannot walk around the rings untill 4 months this is for health issues.

My only warning is its very addictive and once you get the bug there is no going back.

Good luck and hope all goes well would be good to hear how you get on and any probs just pm me