I would love to. I get "The Racing Pigeon Digest" magizine. In it, they had an add for youth only one loft race. 

 it is free, besides shipping bird there. Only 50 birds being raced, limit one bird per person. I am planning on entering one bird. I am soo excited!
but other than that, I don't think I will be able to race any other races. To expensive! I would love to do club races, but the clocks and everything is just a little out of my price range. One loft races are cool, but club races are what I would enjoy more. Because I could train my own bird. Not someone else training my bird.
I think the aviary would work. just as long as you don't have more than 4-5 pairs in one 5×5 section. With a 4×5 aviary section for them. And then a race team not exceeding 12-15 birds, assuming that they have an aviary section as well. It would also be good if the flyers got a toss\loft fly a day. Though, hawks have different plans sometimes.
The landing pad\board is the flat surface the birds will land on to go through the trap door. you were right. If It were me,,, I would build the aviary on the back, the landing pad on the front. If it were me, I would build the front landing pad where there is wire all around it, but a large door that you can open to let the birds out\in to loft fly and come back. Have the traps inside the cage, so they trap to go from the cage to the inside. Does this make sense? If it doesnt, tell me and I will draw it up. this is the best way in my opinion because the birds every single day are getting to go thru the trap. They should be so comfortable pushing through it. Every single second counts in a race! And, if your birds are comfortable with you, on a race day, they will allow you to slowly walk up and close the cage. That way, nothing will scare them out of the cage such as a hawk soaring over, tires screeching, a cat walking by, etc.