Well, I have a group of five players, with one animal companion and now one cohort, and they are of avarage experience with DnD. I have not made any changes to the encounters as of yet and I am not planing to, at least not yet. They are a level lower then what is normaly suggested for these adventures due to the size of the group. This keeps the challenge up for them.
I can see making changes as needed to keep it challenging for the PC's. But keep a feel on how your PC's are doing and then make changes as needed.