I think in the people app you can import into a group but all contacts shows every group contact merged. You can create new groups, besides the family, friends, and business.
Change to the group before you import the vcard file (.vcf). You can also hit the star on a contact to put it into the favorite group. To put a contact already imported into a group, change to the group, add new, start typing the name and choose from a drop list. Or tap the contact, edit(pencil icon), scroll down and click groups and check the boxes of the groups you want that contact in. Haven't found an easy way to mass edit into groups, my contacts were automatically put into a group labeled 'imported'. But they were never organized in the first place.
It might be easiest to sort the contacts on the computer, then export the vcf(s) to the tablet's internal storage over usb, then import into the group(s) you want.