I’m working on a unconventional backup character “WugWug” for an upcoming campaign.  He will be entering an established party at level 7 or 8.  WugWug is an albino bugbear Circle of Shepard Druid that has taken a vow of silence and practices pacifism.  However, he breaks both vows routinely because of his primal nature. 

 So I know bugbear is not an optimal class for a druid but I’m just looking for a little advice on how to make the most out of his racial features as a druid:

• Long Limbed. When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.
• Powerful Build. You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.
• Sneaky. You are proficient in the Stealth skill.
• Surprise Attack. If you surprise a creature and hit it with an attack on your first turn in combat, the attack deals an extra 2d6 damage to it. You can use this trait only once per combat.

Any advice on spells or feats to make this build work? 

Shillelagh immediately comes to mind. That's going to be amazing with your reach. As for stealth and Surprise Attack, and form you shapeshift into that isn't easily noticed could benefit from that surprise attack, assuming your DM agrees.