In a Windows environment, Remote Desktop is pretty much always the best solution for "office" type applications. Depending on what your server environment is, setting up Terminal Services for a few users would be an easy thing to do.
Using Remote Desktop over a VPN is the best approach as you dont then expose the server to the internet. Problem is that a quality VPN gateway like my current favorite plaything the F5 Networks Firepass is $$$$$, as this technology is intended for corporations, but the Fortinet range of appliances goes right down to an afforable tiddler, the
FortiGate Model 50B which
appears to have the same feature set as its bigger brothers, just at a fraction of the scale. Using this box as a VPN gateway, you get a high quality firewall (and a lot more) for free!
Disclaimer: I have no associations with Fortinet other than the organisation I work for will be spending $$$$$$ on their products this year.