Dawn of the Scarlet Sun is meant to be played in a single 4-5 hour block (but has a reputation of having some really tough combats, FYI). I've run Carrion Hill, but I think it'd be a real stretch to finish it in two 4-hour blocks (especially with helping new players). Down the Blighted Path, although I haven't run it, would definitely not be suitable as it's a "deluxe" module intended to take several sessions.
Could I suggest thinking about the Pathfinder Society Quests? They're designed to be played in chunks (if necessary) and are designed for new players.
Carrion Hill can be done in 2 sessions if the more experienced types lead the way. Blighted Path will not fit into that time frame, unless you skip the middle portion as an uneventful trek.
I'm assuming you guys are around level 5, so one more suggestion...
Brandon Hodge's From Shore to Sea could likely be done in 2 blocks.
If these are brand-new Pathfinder players, I'd recommend an adventure for first-level characters... or even one designed with new players in mind
Master of the Fallen Fortress would fit the bill.
Another idea would be Gallows of Madness. This one is a deluxe module, but it's comprised of three short adventures, each of which can be played independently. The first one could be run in two sessions.
If you want a module that emphasizes role-playing over combat, the murder-mystery adventure Murder's Mark is very good. This one has the potential to go very off-script, so be prepared. (Last time I ran it, the group took five sessions to finish it, as the players got interested in investigating stuff that was there for flavor, so I ended up improvising a lot of content.)