Also, make sure the drainage in the run itself is away from your house, as you said the run is attached. If you can use the rainwater for the birds, setting up a rainwater tank could also be an option for dealing with runoff in the area.
Have you noticed how we want to do things more when we can't? For example, I'm a really small eater, I eat when I'm hungry. If I have to fast for a medical test, I'm suddenly wanting full cooked English breakfasts.... There's no motivator like "you aren't allowed to". LOL
Glad your event...
Oh, I wouldn't let you leave LOL (sorry, don't mean to sound like the main character in Misery, it's just I have such trouble making decisions as to how to go about things, let alone getting on and doing them, I'd love to have somebody who knows how to do things so well on my "team". )
My "go to" tool for encouraging movement in a direction is the tossing of food. Something yummy on their ramp and out in the run, and they might be encouraged to give it a go. C'mon Laverne and Shirley, Schlemiel, Schlimazel! Get out there girls!