I recommend
The Haunting of Harrowstone, Vol 1 of the
Carrion Crown Adventure Path, by Michael Kortes.
This is now my favorite "first AP module" in all of Paizo's many Adventure Path series.
A super effort turned in by Mike Kortes as principal author, Brandon Hodge for his
awesome design work on Haunts, and to James Jacobs, Rob McCreary and Wes Schneider for their excellent work in creating the overall story, development and presentation of the Carrion Crown AP. And oh yes, new variant rules for animated objects, too! (by Adam Daigle IIRC.)
I've read them all, played in (or GM'd) most and this gets the nod from me.
A great coherent story, excellent mood and pacing, engaging encounters, strong theme and innovative game mechanics with the new Haunts, as presented by Brandon Hodge and implemented by Mike Kortes.
This module is ENnie award winning material, in my opinion.
Re: The Whispering Cairn :
The Whispering Cairn is my favorite module of the 3.5 era and Erik Mona's sense of pacing in the module is second to none. Erik uses a
very clever bit of design work in the module at one point to force the party to leave the dungeon to go back in to Diamond Lake to "solve" a barrier which otherwise prevents further progression. Top notch design. That said, it is a very difficult module, and for as much that I love
The Whispering Cairn for getting Paizo's revised AP concept on track with a phenomenal module? I might just like
The Haunting of Harrowstone even more.
Certainly, if the goal is to present your first
Pathfinder module to your group and make it fun, you don't need the second guessing that goes along with making the conversion changes nencessary to make
The Whispering Cairn work well with your PFRPG group (In particular, some changes to the way swarms operate in PFRPG and the overall CRs of the final encounters are a little tricky and a design distraction from your first go with
Pathfinder, imo).