Host your own website, make a php gateway that asks you for your password.
Then once it checks your blockchain password, make it ask for a csv file.
Then once it parses the csv into a variable in php, follow the "Send to many" instructions at the link above.
Then have the site show the transaction just in case, then have it ask for your second password if you have one.
Then send the transaction via api.
How coincidental !!! I solved it exactly this way. The only problem was the 'note' param of blockchain.info send to many API was not working. That has also been taken care of...
Yeah you have to format it for URLs, so a lot os %20 etc.