Using TS means you only have to upgrade the one installation, and you don't have to deal with the mess of the database hosting. Costs a bit for the licensing, but worth it in saving you the hassle. Terminal Services is your best bet, and it is easy to setup.
If I set up a Terminal server with Server 2008 R2 SP1 would I be able to access the hosted application from a mac, I don't have any experience with Terminal Services and haven't read the documentation yet.
I would prefer to just do VM's or Terminal Server but most of the Macs are PowerPC and I'm pretty sure that you can't use VMware on that architecture.