Not selfish at all. DD22 and I have always vacationed without DH. He has trouble getting time off (actually he's a professor so he is STUCK from mid-August to mid-May) and honestly he just doesn't love Disney. DD and I have been to Disney too much- 27 (?) trips- and DH has only come with us 4 or 5 times. No worries... everyone knows what works best for their families.
Will it be you, MIL, and 2 kids traveling, or is your DH going too and just not going to Disney with you? Could he purchase tickets with his military discount before he's done... or does the active military person have to be with you at WDW? USAA has good deals,
Undercover Tourist does too, but remember a "good deal" on Disney tickets is usually less than 5% cheaper than buying through Disney.
Price out lots of options. Honestly, if it's you, DH, 2 kids, and MIL, I'd do the offsite condo. SO SO SO much cheaper than a Disney hotel, pretty much just as close to the parks as a Disney hotel, MORE space and privacy. You can also have breakfast much cheaper, and even easy suppers (because who wants to really cook and clean on vacation) to save money there. It's supposed to be vacation, right? If there are 5 of you traveling, it's not going to be much of a vacation, stuffed 5 people into an onsite room. I guess maybe another option would be to rent
DVC points, but that's still going to cost you way more than an offsite condo. If you do stay onsite, we have liked ASMu as much as POP. We like the Broadway buildings. You could check Orbitz for prices. Sign up for ebates, go to orbits through ebates, and you'll get some cash back. Also look to see if there's an orbitz discount code available, as they usually let you apply any discounts they are offering to the cost of the room at Disney.
ixna on the loodba ellingsa...and we never had this conversation. 
