ADHD at UCSB (or UC or other large public university)

My son has ADHD and plans to start at UCSB as a freshman this fall. He is very bright but with poor study habits/procrastination/forgetfulness and coming from a HS with <1000 students and is not proactive and I am concerned about his executive functioning challenges affecting his ability to manage his time as well as his non-academic life and that he will fall through the cracks with the large impersonal lectures and lack of a single advisor. (He was accepted at several small LACs with superb student safety nets but wanted the beach location and social opportunities/parties of UCSB.) Do you have suggestions or do you know how we can know that he is not falling through the cracks? He will get accommodations approved from DSP but they are only for extra time. Thanks.