Just to confirm, you feel you need to accept two ROTC scholarships concurrently in the event that your dream of attending USNA does not pan out - to both Army and Navy? Why - is your decision not yet made between them? is there an expiration date on either ROTC offer that's fast approaching that makes you feel you have to to sign for two offers concurrently? What are your response deadlines? Is it still that you have to respond to AROTC within typically 30 days of the offer, and have until a later date for AFROTC and NROTC - near May 1st? If so, why not sit tight, make your decision in the coming couple of weeks, then sign up for USNA or NROTC if you want/ let Army know you're declining/ have decided to go Navy or let the others know if you decide to go Army. I support keeping the ROTC scholarship in case you need it - it's yours, but two concurrently? Not getting the advantage for you. Why let USNA potentially know that you have accepted the NROTC commission path offer while they are adjudicating your application to the SA? What if admissions sees that and gives the slot to someone who was USNA or bust so you both can be future officers? How does that help you?
Good luck - congrats on multiple scholarships and paths to serve. Thanks for your willingness to serve.