What theotherjonv said – all good advice there
I wouldn’t go for nails myself but that’s up to you. But, please, please, please…when you screw the boards down, can you make sure the screws run in a straight line. If I’m ever having a beer on your deck, I’ll be forced to point out the crooked lines of screws otherwise (I need to get out more).
Two batteries would probably be ok though…don’t really need two drivers do you?
Do you know anyone who could lend you anything around 18V as a driver? Would make life a lot easier. You’ll wear a battery down in no time if it’s a low voltage cordless and you’ll shag the batteries using them after a half-charge (unless they’re LiIon…but too much info).
Finally, if you’re not over-burdened with lots of good kit, hire a decent circular saw for the day – it’ll save you loads of time. Also, if you’ve only got a cheap battery driver, then get a cheap plug in drill and pre-drill pilot holes for the screws (hee hee, this will also make it easier to do them in a straight line…use a piece of string).