What kinds of gloves should be used for working with mortar?
Considering how little exposure you will get to the mortar for your small project, you're probably fine with just your work gloves. Wearing latex gloves under your work gloves will provide additional protection. I would suggest that for the people who will be working directly with the mortar.

Big picture, more important than gloves is breathing protection. Inhaling dry mortar powder can be very dangerous, even in small quantities. Different people have different reactions: while one person could spend years breathing the stuff and never have any problems, another could experience severe respiratory distress on their first exposure. Whoever is opening bags and mixing should be wearing a respirator. The disposable kind is fine, if rated for mortar exposure.