I'm a worrier so I like to REALLY pad my time. Here's my worst case scenario figures for your situation.
ADR is at 12:10 but restaurant is running behind since you're at the peak of lunch so maybe you're seated at 12:40 (I've been seated 1.5 HOURS late at 50s PTC at peak dinner time so don't think I'm exagerating; this is a real possibility and even likelihood). Your server is slow and you want appetizers and desserts figure 2 hours so out of there 2:40. You'll barely even get to the front of the park before your bus is pulling out of Pop.
Lets now say you're seated on time (I don't think it's at all possible but lets just say for the sake of arguement it happens) so you're seated at 12:10. Average meal from time seated until time out the door will likely be around 1.5 hours if you've having dessert or apps or even just participating in the antics so that means walking out of the restaurant at 1:40. That means you're at the bus stop at 2:00 (it takes time to get there and I'm assuming you're taking your time walking at a normal pace since you're now stuffed with all that yummy home style cooking). You're supposed to be at your DME bus stop with your stuff 15 minutes before your bus arrives which means 2:45. This means you have 45 minutes for the bus to arrive, bring you back to Pop, wait in line at Bell Services to grab your carryons (I'm assuming you stored your carryons with Bell Services in the morning before heading to park and I'm also assuming you checked your luggage in with your airline before heading to the park). You MIGHT make it but boy are cutting it close. You're really counting on a lot of factors falling right into place. You're counting on being seated on time, having good service, your bus coming in a timely manner, not having a line at Bell Services and your bus not arriving early. If any of these things happen then you'll miss your bus.
If you miss your bus, will that be ok? Are you the kind of person who can go with the flow and will be just as happy with paying for a taxi to get yourselves to the airport if you miss DME for any reason? This isn't how I'd want to end MY vacation but that's just me. The constant time watching would ruin my lunch experience. I like to end my trips in a much more relaxed manner. If I was the one planning, I'd probably just get a late morning snack at Starring Rolls, leave the park by 1:00 and then get a late lunch at Pop before hopping on DME.
That is exactly what I was thinking after I read people's responses. I already added it to the budget. 
