3 level dip into devotion paladin also works very good with sharpshooter, since you get Sacred Weapon class action which adds your charisma modifier to the weapon attacks for 10 turns. It can offset and even later surpass the attack penalty that comes from the sharpshooter. Paladin skills are also charisma based which pairs well with bard's.
Apart from that, 3 level dip into a battlemaster fighter is great for a sharpshooter, since you get Precision Attack which is a free action that gives +1d8 on the next attack roll
