I bring my dog to the shop most of my shifts in the summer. Here are some positive and negative things that happened:

She is extremely helpful with our mentally ill patrons by putting them at ease.
She melts our grumpy alpha male patrons and turns them into cooing fatherly types.
She interacts with anyone who is socially anxious, is really happy to meet them, and then gives the people around them something else to talk about.

We had also had cases of:

a volunteer being allergic ( I stopped bringing the dog on the days that volunteer came, then they insisted i bring the dog anyways and took antihistamines)
children being scared of the dog (i leashed the dog in the back end of the shop, and sat with her when they wanted to get closer)
A man who was clearly disgusted by the presence of the dog and would not come into the shop until she had been leashed in the back area.

Honestly, having her in the shop is awesome, and the few negative scenarios were individual events that were dealt with as needed.

I would advise you to have the people who would be on that shift meet the dog, and talk about their individual concerns, and then just do it. Waivers are an awful way to instill confidence.

Anibal, from bikeSauce in Toronto