Hi Kimberly!
Welcome BACK to the Disney Parks Moms Panel! You'll have no problems adding
Disney's Memory Maker to your entire Walt Disney World Resort vacation. You can purchase it now, or wait until you arrive in Orlando. And the best part is that it can be shared with multiple people in your reservation, so your cheerleaders will have access to unlimited downloads of their photos as soon as they're taken.
As far as
Disney Dining Plans, they are a length-of-stay-per-hotel purchase, but I do have a few ideas. While I've not added a dining plan to a Walt Disney World Resort vacation post-booking, I'm told they can be added until a few days before your arrival. I'm a bit familiar with your competition, and I understand that you won't receive your tickets or know your room assignment until your group arrives at ESPN's Wide World of Sports. However, double check the luggage tags you receive as part of your Disney's Magical Express reservation as the tags usually include your complete resort reservation number. A helpful Reservations Cast Member at (407) 939-1936 can help you figure out if you can add a Dining Plan with the info from those tags.
If your extended vacation days have you switching resort hotels you can definitely add a dining plan to that second stay. And as an absolute last resort, you can always purchase
Disney Gift Cards as a way to sort of make your own dining plan. A lot of guests love that Disney Dining Plans are a way to pre-purchase their meals, so they can focus on fun and not worry about dining math while on vacation. Disney Gift Cards are accepted at almost every dining location and can even be used to pay off the balanced charged to your MagicBands.
I hope this helped and We'll See You Real Soon, Kimberly!
~Kristen