Rabbitbait
Grog-nerd
They're about to enter the Howling Hatred at 5th level - only three of them though. But they'll have 3 NPC birdmen to help. Even then I might have to make it a little easier as they are missing some punch. The book suggests 6th level, and they could probably handle it if they were at full numbers, but with only three guys and some bird guys...I dunno. Very iffy.
Don't do it! Seriously - if you make this part easier, they'll probably end up heading down to the fane of the eye (or whatever it is called) way earlier than they should - or heading straight to the water temple through the link.
This module is so interlinked and so easy to move into challenging areas that if you make any part easier, you'll end up having to do it again and again until you finish the entire plot at level 10, or have them with no chance to escape a TPK.
Better to send them into an area where they are slightly overmatched so that they can get out with minimum casualties, then regroup and replan. You never know, with only one level difference they may do fine anyway. That said, I would play up the roleplaying opportunities and try and reduce the number of fights they are likely to get in, and I would play up the things that would hopefully help them realise that they are in trouble, before they get into a fight.
I say this, it didn't work in my game. Ouch.
All just my opinion of course.