I just took my first Skybus weekend jaunt and they did indeed announce pre-boarding, but only once. You have to be pretty quick b/c they'll quickly call group 1 almost immediately thereafter. Just stand fairly close to the door when it's almost boarding time and wait to hear the announcement then enjoy the pre-board. You may have to push your way through the crowd a bit, but you'll do pretty much anything for Grandma, yeah?

Also, Skybus will provide wheel chair service. At BUR and CMH, the "front" of the plane is loaded with a ramp that does not have stairs, so a wheelchair can go up to the door of the plane without a problem much like when using a real jetway. You can request a wheelchair by adding a note to your itinerary, or there should be a luggage attendant who can call one for you.