You'll definitely need to find out what the ISP here will allow (PPTP is the main issue, if I remember correctly), and how flexible your VPN administrator is. Your admin can tell you what questions to ask the ISP. Issues like changing server IPs make VPN admins very unhappy. :-)
Another tidbit, which probably doesn't matter for your business but I just went through it so I thought I'd share. To get a document notarized here, so that it is recognized as legitimate in the states, you have to see the Consul at the American Embassy. She and the staff were very helpful, and it was $30 for the stamp. (There is actually another option, but it involved getting a Belizian court to approve a Belizian notary, which seemed more complicated to me.) There were specific days and hours for American Citizen Services at the Embassy, so check before you take the ferry over.