Depends on the size of the group. But regardless, you're likely going to want to get the flash off the camera, meaning a light stand, modifier (softbox or umbrella, the latter is cheaper) and a way to trigger the flash. Basically, at the distance away your flash would be to light a group, the modifiers you linked won't give light any softer than a bare flash.

For two people, a 24" softbox is ok. Larger groups, with a speedlite for power, you're probably looking at more than one flash.

I'd suggest reading Syl Arena's "Speedliter's Handbook" as a great place to start.