The loser in this transaction is not the credit union, it is whoever is accepting credit card payment for cash equivalents. The seller is giving you cash at 100% face value but getting back 97-99% from their credit card processor. Or are you saying the credit union is the one making the sales?
Also, spreading your deposits around is a bad idea. It could give the appearance that you are structuring (a federal crime) your deposits to get around the CTR reporting.