Since both of your trips are 5 days, I checked the prices for Annual Passes and the 10 day non-expiry MYW tickets. It looks like you'll save the most money with straight Annual Passes, if you don't want to use any plusses (like water parks and Disney Quest). But if you plan to use a couple of plusses, you may be better off getting the 10 day non-expiry MYW tickets with 5 plusses and park hopping instead of the Premium AP.
Annual Pass (adult w/DVC discount): $314.18 (w/tax)
Annual Pass (child w/DVC discount): $267.32 (w/tax)
10 Day (adult) No Expiry MYW w/Park Hopping $337
10 Day (child) No Expiry MYW w/Park Hopping $302
Premium Annual Pass (adult w/DVC discount): $415.35 (w/tax)
Premium Annual Pass (child w/DVC discount): $353.58 (w/tax)
10 Day (adult) No Expiry Premium w/Park Hopping & Magic Plus (5 Visits) $358
10 Day (child) No Expiry Premium w/Park Hopping & Magic Plus (5 Visits) $324
For your son's friends, you may want the 5 day MYW tix that expire. If the boys will want to go to the water parks and DisneyQuest, you'll want to get the plusses and if you plan to park hop, then you'll want the hopping option.
5 Day (child) Expiry MYW $156
5 Day (child) Expiry MYW w/Park Hopping $188
5 Day (child) Expiry MYW w/Magic Plus (3 Visits) $198
5 Day (child) Expiry Premium w/Park Hopping & Magic Plus (3 Visits) $232
5 Day (adult) Expiry MYW $196
5 Day (adult) Expiry MYW w/Park Hopping $225
5 Day (adult) Expiry MYW w/Magic Plus (3 Visits) $233
5 Day (adult) Expiry Premium w/Park Hopping & Magic Plus (3 Visits) $268
Also, if the boys only want to do one plus -- say go to DisneyQuest one day, then you'll likely save money getting no plusses on your tix and purchasing the tickets for DisneyQuest or the water park separately.
If it were my family, I would purchase the regular Annual Passes for my family and the 5 day Expiry MYW with Park Hopping for the friends. Then I would get the boys discount tix for a trip to DisneyQuest or one of the water parks, separately -- I believe that would be the lowest cost option if you park hop (as we do) and if the boys want to do one plus (I'm assuming they are at the age where they would want to do DQ or a waterpark).
For information on purchasing Annual Passes with the DVC discount:
http://www.allearsnet.com/pl/apass.htm#dvcapfaq
All of the MYW tix prices I've given are the discounted prices available to subscribers of the Mousesavers newsletter, which is emailed to subscribers on the 15th of each month. Subscribe here:
http://www.mousesavers.com/newsletter.html. You must follow the links from the newsletter to get the discount price from Ticketmania or Discount Orlando Vacations.
I've never used the vouchers, but I think they are being phased out. I do have the DDE card and found it easy to use. My family saved $75 over the course of 6 days at WDW on our recent trip. Since we'll be back for two more trips in the coming year, we'll save a bundle with DDE.
I hope this helps!