Went in 2011.
Drive. Much cheaper and more fun doing a road trip as well as attending a foreign GP.
We went with bronze GA tickets for the whole weekend and were staggered at how big the circuit is, takes AGGGGGGGGGGES to walk from one end to the other, well it seemed like it for us anyway as it's quite elevated in parts which I guess makes it more tiring than if it were flat.
I found a place half an hour south of the circuit, some fancy B&B in a quite village (well actually a hamlet of sorts) it was well and truly out of the way, but it was beautiful and peaceful.
If I did it again I would definitely get hotel accommodation nearer the circuit so I could soak more of the party atmosphere up.
As for your choices definitely caravan it, it's what it's all about imo! Either that or a closeby Hotel to enjoy the circuit and everything going on being not too far away.
As for viewing spots you do not have to get up early on Friday, so relax on that one, we strolled around and got a seat on Kemmel Straight with ease and we were no where near first people there. Saturday is slightly busier but we walked around the circuit between FP3 and Qually, and as Qually is on for an hour we didn't mind standing up on the kemmel st (friday we could sit cos of the space)...
Sunday would have been heaving up there though as I could see from the tv screens, so we just stayed near to our car park entry at the south of the circuit and watched at pouhon (which was good anyway as fancied a change from just watching the cars just go in a straight line
Spa has it's own micro-climate so bring a coat / umbrella and suitable comfy weatherproof foot wear... also i'd buy a kangaroo tv next time I go, and try to go to the toilet before going to the circuit, as the portaloos are horrific.
Make a packed lunch if you can (places will charge £6-8 a burger), cheaper and healthier, but do try the belgian waffles, best waffles ever, and mayo and chips yum