Wow that's a loaded question Mate... It's not that simple. To proceed could you tell us;
1) The skill level with the use of airbrushes. (None-a little-expert)
2) Will they be using the compressor only for airbrush work. (Do the spray any solvent based paints requiring a larger spray outfit?)
3) Where will the finish work be used. (outdoors, inside on display)
Not all acrylics are the same. Many sold for airbrush work are die based
and will not hold up well under UV (sun) light. Pigment base acrylics work and last the longest exposed to natural sunlight.
Help us out with a little more information and I'm sure most artists have an opinion on what would work best.
A final and important thought; How much can you spend? Top of the equipment costs some big bucks, but you can still buy quality for a lot less with a little help and knowledge.