if I were in your shoe,s ,depending on the distance you want to go out to ? get some training into them on the line of flight ,start at 10 mile ,when coming straight home ,increase the distance ,maybe a local trainer who takes other birds would be good , teaching them to "break for home" ? I would send the latebred hens to the first couple of races (personally think hens are more "hardy" ) then the latebred cocks ,giving all the latebreds around 4 races this season ,then put them bye for next year .the older pairs could then complete your old bird racing . I wouldn't breed , I would let them nest but not hatch ,putting pot eggs under ,separate after first race .that's the way I would tackle it , others may say different .good luck racing