If he's near a base, there's always the option of the ITT office on base too. I feel like the rules for those vary based on the location (for instance, DOD Contractor's are available to purchase from my local base ITT, but may not be at others, the rules were updated since our base is so heavy with contractors). The tickets from ITT tend to be just like ones from UT or AAA so anyone should be able to use them with out proof of service once at the WDW (but whatever requirements for the office would be needed at purchase). IIRC The Military Salute ones are the ones that the proof is needed at the gate/ticket window at WDW at redemption/first pick up/activation, but as long as he's with your mom at the time, that shouldn't be a problem (if eligible). I've bought from ITT before w/o issue, but even with my father eligible (disabled vet) for the other style, I wouldn't be able to use them b/c he does come/go to WDW with me.