I'd put the 5 healthy ones into the cycled tank. Treat the ill bettas. When they are both
healthy, plan their introduction into the sorority.
*Acclimatize the newcomers to tank water before they go in - by adding tank water to their cups. Feed the new fishes a snack just before they transfer.
*I would do it at a major water change/vaccumming/cleaning and re-arranging.
That way the established sorority is 'thrown off' by major enviromental change.
*Take the sorority out of the main tank into a bucket of tank water. Reverse pecking order, so that the Alpha female goes in the bucket last
. Feed the sorority a snack, while they are in the bucket. (All the girls should have eaten before they meet, so that the competition for food is not an immediate issue)
*Slip the two new bettas into the main tank while the sorority. Give them about 20 minutes to orient themselves before the sorority comes in.
*Add the sorority back, again in reverse order, so that the Alpha betta goes in last
*Watch for any overly aggressive behavior. Any problem should make themselves known pretty quickly (I had one little girl betta that aggressively went after another older betta twice her size... as soon as they both hit the water!).
*Isolate any aggressive fish... float her in a clear container or net cage for a few days. If she doesn't mellow out at the next introduction attempt, she may need to be rehomed.
Good luck healing the girls and with your sorority!