The access anywhere will require either VPN or a server that is accessible from the Internet. This can be setting up routing through your router or adding another NIC which is setup on the Internet directly. Lots of possiblities.
I personally would go with the SQL database since I believe it gives you more flexibility and power. Especially if you want to have reporting and Excel connectivity, with SQL you can setup your excel spreadsheet to connect directly. I would also look at SQL Reporting Services, with these you can setup live reports and charts which may be what you are thinking of doing with Excel, but with SRS you set them up once and you can view them anytime via a web browser.
Do you need browser based forms or are you going to use InfoPath as your client. If you need browser based forms then that would be one reason to look at SharePoint.
Have you looked at the Database Accelerator diagram? http://www.qdabra.com It shows how InfoPath and SQL can be tied together to provide a complete foundation.
Hope that helps.