Haven't been on this site for a few years, but your question caught my attention. The first main event typically takes place on Monday and is the parade where the seniors "separate" from the rest of the wing. Tuesday is reserved for commissioning and is a "must" for parents and close family to attend (attendance is sometimes limited due to constraints of the facility in which it's held.). Those events typically are in the late afternoon and early evening of the night prior to graduation (again, likely Tuesday night.). Graduation is typically on a Wednesday and you'll need to get to the stadium early....like 7:30am or even earlier if the speaker is President and security is ramped up. Graduation ends around noon, but graduation parties (with parents) take place that evening. Plan to leave COS on Thursday. As to when to arrive in COS, Monday is the latest. My two cents is "your child is graduating from a service academy and saved you a boatload of money in tuition." It's time to celebrate. Treat yourselves to a couple nights at the Broadmoor....Friday and Saturday prior to the graduation. Then transition to something like the Marriot Residence Inn for Sunday through Thursday. Or, look for a VRBO depending on your family size. Enjoy the week in May!