First off, MIT is not an Ivy League school. Secondly, you would not be transferring to MIT for post grad, you’d be applying to a MS program. It is very competitive as you probably realize.
My advice is to go to UC Riverside and be the best student you can be and enjoy your college experience. If you go in to college with the goal of trying to get somewhere else, you will not be happy. Congrats on your acceptance to UC Riverside!