Cornish X for meat bird trio at a local county fair

[dmgaqua]

My 12 year old son wants to show at the local county fair the "meat bird trio". I use to do this many many years ago so I am out of touch. Can anyone give him some pointers? Where to get the best chicks? When should we get them to show at the fair the first 2 weeks in August? What is the ideal weight? Males or females? Any other pointers? Thanks in advance