Congrats on going back to school! Your timing will be fine. I just finished my 1L year at 30. I wasn't the oldest in my class by a long stretch. Another of my colleagues turned 40 during the year. One of the (recently graduated) 3Ls was nearing 50. So far, I've had nothing but positive feedback from potential employers - there's something to be said for a resume with substantial experience on it.
I estimate i will be 28 when i graduate UG and probably 31/32 when i finish LS. Will i be too old? Anyone else my age?