I think you are good to go.
In reality, those potential SMB at 4-6" will never be able to eat those current bluegill 4-5". The bluegill will quickly reach a size where they won't be "eatable" by the SMB, and the SMB's growth rate will never catch up.
Get lots of pictures if you go with the SMB from Kansas. I might have to make an order also.
The other thing that you are doing is trying SMB in a pond without maybe their best forage. We don't know if Bluegill are a stable backbone of forage for SMB yet.
You'll have the option to put in Golden Shiners at a later date also.
