Sounds like you have already made up your mind as to which job you will take. Think it over very carefully as sometimes money isn't everything. Although, if it is just a summer job and you are not going to make a career out of it then I would go for the money as well.
You can always tell the company you don't want to work for that you still have several more interviews set up and you will not be able to make a decision until these interviews are complete. This lets them know that you are taking the time to choose the right job for you and that you will need some time. Usually, they will be in a hurry to fill a summer position and will probably tell you that by the time you make your decision the position may be filled.