Booking Trenitalia for a Group

I have a two-part question here: First of all, what's the easiest way to purchase tickets from Trenitalia for 6 people? It looks like it limits me to 5 per purchase - do I just purchase 5 then hope that my additional person actually gets the next seat (I know it has a "seat near..." section to request a close seat, but...) On a side note, is it even worth purchasing ahead of time? I'm trying to get them as cheap as possible, so one trip we're trying to use Sabato Italiano fares (requiring THREE purchases!), and I'm worried that those will sell out. It already tells me that some of the earlier trains don't have that fare available on that Saturday. The mini fares are pretty tempting, too, and those sound like they sell out as well. On the other hand, I've read that it may be possible to get a discount for our group of 6 adults, but that's relatively old info so I don't know if that's even valid advice. Hopefully these questions haven't been answered a million times, I couldn't find the answers myself. Thanks!