I take Ritalin myself, and have no personal experience with Vyvanse. This is one of the newer meds for ADHD, so there aren't a lot of threads on it. But I was able to do a search on this board, and came up with a couple of threads for you to read:
10 year old and Vyvanse
how long does vyvanse stay in system
Perhaps othters will chime in here with their experiences.