There are a few threads on sexing Bluegills that might be helpful. Here's one.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=21505Even if you aren't perfect at sexing them, it should be better than just stocking by numbers and hoping for the best. Hopefully, one of the pros will be along that can comment on whether you want a 50/50 mix or maybe more biased towards one sex.
Keep us in the loop and let us know how it goes,
Bill D.
Edit: What predator are you stocking to keep the CNBG population under control or is your plan to use this little pond as a forage pond for the main pond?