Is 4GB ram enough for what I want to do?

I am buying a 13" MacBook Air for sixth form to do my work on. This means I will be using the laptop to do simple tasks such as writing documents, spreadsheets and powerpoints etc.
I will be doing a lot of web browsing and watching youtube videos and using google drive.
I would also use the laptop often to run iPhoto, rosetta stone and also to play Age of Empires 2.
If it makes any difference I will be using iTunes a lot as well to sync between my mac and iPhone.
Although a situation in which I would need to do all these things at the same time probably wouldn't arise, I would like it to be able to so, so there is always some 'buffer memory' if you like.

Will 4GB ram be enough for me? Or do I need to go for the 8GB ram option?
Thanks

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