There are other bitless options available besides the sidepull (Google Image Result for http://www.galadriel.shaftnet.org/horses/duchess/jumping-hackamore.jpeg
) and the hackamore (Google Image Result for http://3.bp.blogspot.com/_TN_TvoKQItc/S80sabvq_nI/AAAAAAAAAOQ/noQZJDWX5j8/s1600/hackamore.png
You could consider an indian bosal (Google Image Result for http://www.fast-autos.net/diecast-cars-models/diecast-car-image-large/rope-bitless-bridle-hackamore-indian-bosal-side-pull_320506094407.jpg
), with or without extra nose knots. It works much like a rope halter, but with better steering. If you choose to get one, make sure to choose one with metal rings, not rope loops, for the cross-under straps to pass through so there's less friction, giving better release.
Another option to consider is the cross-under bitless style (Dr. Cook's, Nurtural) (Google Image Result for http://www.naturalhoof.co.nz/pictures/bitlessbridle300.jpg
). Beware though, the release can be slow on this bridle,and some horses don't like the 'whole head hug' action. It's up to you though, it may work in your situation!
There is also the lightrider bitless (Google Image Result for http://www.lightriderbridle.com/uploads/3/6/0/3/3603905/4812848.jpg
), which is also pretty mild, basically just a step up from a noseband with rings.
The LG Zaum (Google Image Result for http://equineink.files.wordpress.com/2008/03/lg-bridle.jpg
) is another to consider. It is basically a hackamore with virtually no shanks, so it does have leverage, but very little of it. This is the bridle that first came to mind when I read your situation.
Explore all your options and choose the bes for you. Good luck!