No signing ceremony and no need to attend the event with your congressman or your local USMA parents club...nice to do but not necessary.
The paperwork will come out in waves. A lot of it is done on line. The big one is the eQIP for the security clearance--and that takes a lot of concentration and quiet but the woman who sends the email whose name I won't share here, is accessible, supportive, and easy to work with. You will need to be finger printed as part of the process.
The last little bits like dental x-rays (you will need a panx) and your vaccination record--do not take very long at all.
The police record check, you can call and then walk into your local/home police station. It does not take long at all.
Really, it comes out in bits and you have plenty of time to complete it.
After you are appointed, if you are going to disappear to Bhutan or do the Everest Base Camp trek for four weeks in April, which would be ideal climbing season, you would want to let your admissions officer know--"Hello, I will be travelling from xx April to Xx May". The reality is, it just needs to be done by R-Day.
Although really, the eQUIP, you will want to do that as soon as you can and not leave Mrs. D waiting.