Changing my field after having started my project for my thesis
I spent half a year working on something which I did not enjoy and had no expertise in because of making the same mistake. It's not as bad as it sounds. Sure, it's not nice, but half a year or a year is a manageable time and doing this could also be a good learning opportunity. Still, it would of course be better if you could change of course.

To what extent did you discuss the original idea with those two professors? Do they count on you, have administrative loops been taken? If you have only talked on general terms about possible opportunities, it would probably be OK if you back out politely. They will understand that an undergrad can change his interests.

However, I would make sure that you are sure of another project before you discuss it with the old professors. You don't want to be in the situation that you cannot find a new project and have to return to the old project, because they will feel 2nd choice. So, I would advise you discuss this first with the professor where you want to do your new project. Explain the situation, be open, and ask him for advice.