Unfortunately raccoons can go about anywhere a cat can. They can climb just about anything. They do have the ability to jump, but the way their weight is distributed they are not good jumpers (typically). I could not find anywhere what the vertical height is that a raccoon can jump. They don't have the ability to leap or jump as high as a healthy cat.
You may be able to hang the shelter from something that the cats can jump into, but that is hard for raccoons to do so. If a raccoon has something it can climb onto to jump into the cat shelter, it will try to jump. So, if the shelter is supported on some type of pole with a base that a healthy cat can jump into, hopefully a raccoon will fall if it tries to jump. They don't like falling downward so after a couple miscues they typically will quit, especially if they don't smell food.
The raccoons will mainly be attracted to food, but if cold they may be looking for shelter too. Raccoons are primarily nocturnal so feed the feral cats during the day and don't leave any food in the shelter late at night to discourage the raccoons.
Here is the link to a document that shows a seemingly foolproof shelter/feeder for feral cats that keep raccoons out: