How to run a current browser on older MacBook

I have an older macbook that tops out at Snow Leopard. That is, this is the limit of OS X that it will run.

Current versions of Chrome and Firefox are not supported for Snow Leopard (10.6) Lion (10.7) or Mountain Lion (10.8)

This machine is mostly used for surfing the web while semi-watching TV.

I am concerned about maintaining reasonable security while surfing.

Options:

1. Run another OS: FreeBSD 8 is supposed to run on MacBook Pro, but that puts me 3 major releases behind current. Mint Linux is another fairly lightweight version. I'm quite content to run a simple window manager (In my Linux days, I used fvwm by preference)
2. Strip Snow Leopard down as much as possible, run VirtualBox in it, and run an OS in that. Set up the mac OS to be in bridge mode, and be unaware of the internet.
3. Set up MacBook Pro as a VNC/Teamviewer and use one of my screens from my Mac Pro upstairs.

Option 1 is apparently difficult to get a usable workstation on it.

Option 2 is not clear what can be stripped, shut off, etc.

Option 3 needs directions on how to safeguard the MacBook Pro to allow only local networking, with no or very limited access to the world. It has the advantage that I am still working in a Mac user space.

It's not clear to me what the relative merits of each of these approaches is.

What are the tradeoffs of these approaches.

Is there a 4th approach I'm missing?

I have multiple computers and the original machine I was asking about indeed will run a newer version of the OS. Curiously, if you click 'software update' it does not report this as a potential update. It's installing as I write.

I have accordingly rephrased the question in light of the next older laptop, as the repurposing of older macbooks is a field of significant interest to many long time mac users. At this point I'm leaning toward the TeamViewer approach.