Avoid the topic of Shivan society completely. Leave them a mysterious force. The stranded group doesn't have to fight them all the time (the Shivans may not even care after initial contact), find new things to play with. New friends, other races, leftover NTF, HoL, SOC, GTI, whatever. The Shivans in this situation become the background noise, a constent annoyance of which you learn nothing. Hell, you might even meet someone who claims to know, but they never get around to telling you the answers you want to know. Mystery is what makes the Shivans interesting, let's not muddle it up with lots of wild speculation.