Just a couple of tips:
Play up how nice and friendly Po and his Wife are, he should be really interested in the PCs and generally be as jovial and nice as you can roleplay. Another great suggestion for the tea scene is for him to call for a toast "To the Pathfinder Society...", making it more likely for the PCs to drink it (since there will always be some slightly meta PCs)
The final combat with the Aspis after the sonic trap is a BRUTAL, crazy melee, so enjoy!
Oh and Besai is a jerk, make sure he is an equal jerk to all the PCs, so they band together against him.
Hope these help