Since it sounds like you don't want to run your own bitcoin node (which would probably be safest), look at payment API's offered by some of the online wallets.
Here are some I found, in no particular order:
http://blockchain.info/apihttps://www.instawallet.org/static/api.htmlhttps://walletbit.com/docs/api/sendhttps://easywallet.org/en/apiPlease check the security and terms of these sites before depositing lots of coin!
I would suggest depositing enough to meet your payment needs for a few weeks or so. Collect a payment address from your user, and initiate a payment to it via the API. Be prepared to gracefully handle the situation where your account does not have enough to pay (probably you'll want an email notification so you can refill the account.)
To avoid paying a lot in fees while still allowing your users to receive their payment in timely manner, you will probably still want some minimum payout.
EDIT:
https://coinbase.com/api/doc -- Looks like they support payouts to an email address, which could be handy.