One thing your party lacks is a rogue. The problem is that the rogue class is very weak. The unchained rogue is a big improvement, but still pretty weak. That being said there are some good rogue alternatives. One of the best is the archeologist bard. Halflings get a bonus to both DEX and CHA both of which would be very useful. Go for a finesse build maybe even going as far as taking fencing grace to get DEX to damage. Pretend to be a child and totally fool everyone. With bardic knowledge you can be the know it all snot nosed brat, except you will actually know it all.
A gnome would also make a good archeologist bard if you want to focus more on the magic. Bards get a lot of illusion spells so the gnome bonus would work extremely well for this. They also get extra rounds of performance which an archeologist can always use.