I'm late on this thread, but I just wanted to wish you guys luck!
And a dog is never too old to have fun with agility! I have no idea about competing but I can't see why not.
As for "attention", I did pretty much all of the techniques mentioned. Starting with the method Tessa mentioned, just waiting for eye contact than rewarding and eventually during certain activities I expect their attention the whole time, so when they weren't paying attention on leash I'd walk away, of course they got a little jerk, praise as soon as they were paying attention again.
I think once Messina realizes what's going on and what's expected of her, gets used to the whole situation, you'll see how quickly she understands that she has to keep her eyes on you at all times.
Good luck again!
PS- That was a great vid Tess