quickbooks over wan

I have a project in which i have to connect 12 Offices (situated in different cities) to a parent server for quickbooks. i want to share quickbooks data file (installed on server) over wan so that other offices can connect and work on it at once. i tried a couple of VPN too, share files and browsing work well but as i give path to quickbooks (on client side)to share company file (share on server), it helds and speed goes down. Then I tried Terminal Server. (through remote desktop)It works well but no one can print locally attached to his computer.Please suggest the best and fast solution for this, that 12 office can work at once but should not have issue of speed or transaction.
Regards
Salman (Soltuion Provider)