I'm not sure how OT will be viewed, but I doubt it would be considered negatively. As far as volunteering, there are many opportunities that are as flexible as your schedule will allow. Afterall, you will be a "volunteer" and not an employee. I have ZERO research experience and not a whole lot of clinical time, but I think volunteering in a hospice setting helped compensate for that. I think hospice volunteering is a "high yield " experience and can help you better understand early on the experience of dying patients and their families. Many physicians, not to mention medical students and premeds, have a tough time with the issue and would rather not confront it until forced to. Taking the time to learn about it as a premed should make a good impression on admissions committees. I volunteer about 3 hours a week on my own terms. The hospice administration stresses that the volunteer be confortable with both the time they put in and the setting in which they volunteer. If hospice isn't your thing, I'm sure that other clinical settings would have a similar philosophy. I guess the bottom line is do what you are capable of in the realms of volunteering and/or research while focusing on what may be viewed as a more important initial
discriminators such as your GPA and MCAT.