Server 2012 and Hyper-V is a good but expensive solution. It would require a new server, hardware and software, and they would have to buy remote licenses and possibly regular Cals given the number of persons who would need access.
Given what is already in place should be able to meet the need, I stick with my recommendation. One thing is to make sure that both computers hosting AC (the Win7 and SBS2011) have enough RAM.
Another thing I ran across recently was WHS remoteapp2011 (try this link
http://www.theofficemaven.com/products/whs-remoteapp-2011 )
One question I have about it is whether it would require RDP licenses or it is separate from the Windows system? With this app, he could simply publish a link on each of the computers and remote to the AC system on the WHS home server.
