I find giving him a paper wallet to be the best option at the moment, as the birthday is coming up real soon. Did a quick google search, and there seems to be a lot of sites where one can order paper wallets from, but rather I'd like to use my own printer and put that piece of paper in an envelope together with the birthday card. I'll do some more googling, but if anyone want to point me to relevant resources please feel free to do so.
By the way, is it possible for my to buy say 1/4 of a bitcoin, or must I buy a whole bitcoin and split it up?
Definitely, print the paper wallet yourself.
Go to
https://www.bitaddress.org and click on "Paper Wallet". Print out one or more and then send bitcoins (or a fraction of a coin) to the address on the wallet you are sending to him. I recommend keeping a copy so that if your friend loses it, you can still recover the bitcoins for him.
Others will warn you about security and such, but this is a gift and the chance of losing the bitcoins to hackers is low, so don't bother with precautions that seem excessive.I just think that printing paper wallets online would always have security risks, no matter who you're printing them for, if the key is compromised then the only gift someone would receive is a piece of paper worth nothing, especially if that someone is new to bitcoins and don't know how to transfer them to their wallet right away and by the time they do, it is possible that the hacker might have already wiped it clean.
So even though these precaution may seem excessive, I am still going to recommend that OP downloads the source code from github, verifies the download, takes it offline and prints the paper wallets there. And I would also print a little set of instructions in the back, telling them how to go about redeeming them. Using electrum wallet would be more than easy and it has a sweep key function.