Hi, Vicky!
You are going to love the
Disney Dining Plan!
Regarding paying for other Guests' meals using your own Dining Plan entitlements, take a look at page 6 of the Dining Plan pdf I included above. The first Frequently Asked Question states that you "may
not use your Disney Dining Plan to redeem meals for friends or family members who are not included in your reservation of have not purchased a Disney Dining Plan."
When we think that we'll wind up with an additional Table Service entitlement, I always make sure to book one Advanced Dining Reservation at a Signature Dining location, using 2 entitlements for one meal. It's one way for us to splurge a little without feeling guilty, and we get to sample some absolutely phenomenal dishes which we would never have been able to try otherwise. Take a peek at the menus of The Hollywood Brown Derby, Le Cellier Steakhouse, Flying Fish Cafe or Fulton's Crab House, all of which are our family favorites (all of which we only enjoy if we have an extra Table Service entitlement!)
Have a spectacular trip, Vicky! Be sure to send more questions as you think of them, too. We love to help!