Well, in the video game they head back to Restov IIRC for a big celebration and formal recognition.
As well as the swordlords, members of various noble houses would certainly take notice, particularly if one or more of the PCs were associated with them. The Swordlords might not like some of them, but I doubt they'd try to deny them a place at said celebration.
Frankly you could have a lot of fun period with any organization that makes sense to you sending an agent.
If one of the PCs is a halfling, maybe an agent of the Bellflower Network asks to talk to them in private about helping halfling ex slaves find a home.
The Pathfinder Society might be curious and offer some help in exchange for notes about discoveries in the area, maybe eventually making a lodge.
Kyonin's government has eyes on some River Kingdoms and might reach out a diplomatic hand to the PCs if an elf or even Half elf seems open to letting them search for old elven sites etc.
Certain religious figures might also express an interest in spreading the 'good word' of whatever deity they follow. Again, a lot might depend on the PCs in your gaming group. If one of your PCs is a known Paladin of Iomedae, it's less likely the temple of an evil goddess will ask him or her if it's okay if they go handing out pamphlets in the new settle ment some time ;)
Get elves and dwarves involved as well, like the Dwarves of nearby Brunderton. Added a fallen Dwarven empire in the area, and the refugees that left, but remember its glory.
Kingmaker is about working with all sorts of groups, after all.