A VPN simply gives you the ability to link in to a network from another network. Nothing else changes - if they can do it on the work network then there is a way to do it with VPNs.
Your first choice is the nature of the VPN - IPsec, PPTP or OpenVPN. Which you choose will depend on the operating system(s) the client(s) use. Your simplest option, in terms of client behaviour, is to use a bridged VPN so that the clients appear to be on the internal network.