If you're going to use a "web wallet" API, then I think blockchain.info is definitely one of the better ones. But, most of the web wallets have an API you can use, just try a few out. inputs.io could be another option.
Thank you. I am not aware of other web wallets with a good API for sending bitcoin. I will definitely try blockchain.info first because it looks good. What other web wallets have this same functionality?