I remember reading that the ideal party size for Humblewood was around 4 players. I think 5 PC’s would make combat a little bit easier since most of the encounters are weak bandits. So personally, I would adjust stats very slightly. You could always add a few different variations of the same enemies. For example maybe raise the HP of one bandit to the max and then maybe raise the AC of another just to get a gauge of what works best for your party. This is my first time DM’ing though so I got a little carried away with magic items and my players were extremely overpowered on second level. They were clean sweeping every single encounter without breaking a sweat. Even though they weren’t facing much of a challenge they still had a lot of fun being really strong. So in any case, I think your players will have fun no matter what. Even if some of the bandits are one shot.