Letter of Recommendation Question

One of my family members knows a 3 star general in the Air Force and he said he would love to write a letter of recommendation for me. I have 2 questions: 1. How much does USNA value recommendations like this? 2. Would it be better for him to email the letter directly to the academy right now or should I wait until I get my candidate number and have that as one of my letters of recommendation. Thank you all for all the help.