Hi Mark,
Firstly, congratulations on your impending marriage! I did the same a few months ago, though no matter how hard I begged I wasn’t allowed anywhere near a Grand Prix for our honeymoon!
I went to Spa last year and camped at L’Eau Rouge (next to the river which gives the corner it’s name!). We rode bikes from there to the circuit every day. So while I can’t give any pointers on where to park your car etc, I can certainly tell you that you’ll be able to lock your bikes up within about 10 metres of any entrance to the circuit.
Depending on the route you take as well, it’s reasonably flat, but I’d recommend sturdy shoes once you’re inside as it’s remarkably hilly.
You’ll have a great time – I’m very jealous (though I’m off to Monza this time next month!)
Enjoy newly-weds!