I was 33 when I started my engineering PhD at a top-5 program, and there is another in my research group who was 35. Grad admissions are very individual, with relatively few admissions made by the department and most made by individual advisors. It is quite probable that some advisors will shy away from older students... but only some, and it is not possible to avoid all prejudices. There are some professors who will avoid or prefer women, or asians, or grads from certain schools, and yet that does not stop people from getting accepted in general.
Concentrate on getting the undergrad. If and when you finish you can worry about your MS or PhD chances.