I think you guys should check out http://www.opswat.com/ there are 2 or 3 products that may be a match. I think that OESIS Framework at http://www.opswat.com/products/oesis-framework provides a single interface to many antivirus and AVG is in that list. Another option is, I think, Metascan at http://www.opswat.com/products/metascan which is more for ISV.
I also found that AVG is certified by OPSWAT at http://www.opswat.com/certified.
I hope this helps.