Air will do everything you want, and battery life is great.
Phone apple and chat with them. I got a free upgrade to 8GB when I told them my needs, and paid for the 256GB HDD. Very happy. It easily has all my apps open, streams movies to my TV via airplay, whilst letting me browse the web on my knee.
Very impressed, WAY quicker than my Vaio, never crashes, just does what it should!
The only downside to it is limited ports (only 2 USB, so I bought a VGA and Ethernet adapter though) and no DVD drive (so I bought an external one). All of these take up ports though, so a USB hub may be worthwhile. 99% of the time I don’t need any though.