I know it's rude, but......

[MommyMK]

My SIL and BIL are locals who cannot commit to meals with us 6 months in advance. They come with us when they can and we ask that they be added when we walk up to check in. We have never ever had a problem or been refused, but they go into the situation knowing they might be told no and are ok with eating somewhere else if that is the case. But it's never been a problem.

 

[TJA]

Same situation with my parents one year. They decided to meet us in Disney for a few days and I already had all of our ADRs set up (without them...). We had no problems at the podium when we asked if they could join us.

I think a lot depends on the time of year and if the restaurants are booked to capacity. As someone else noted in this thread, they have to abide by the fire code, etc. However, at slower or "normal" times of the year, most restaurants are not at capacity.

 

[merina888]

Given that it's an event during SWW, there is a very good likelihood that this event will sell out which would mean that the OP would not be allowed to bring in an extra person, and that includes anyone under 2 years of age due to fire code. So they'd have to choose who'd not get seated or forgo their ADR and pay the $10 per person charge. For an event like that, no way I'd risk it. I'd keep looking and cancel if I couldn't.

 

[dpswift]

Once you get closer more will open up. Last night in one hours time I got Jedi Mickey and the Galactic Breakfast for next week. There was another breakfast available this morning. That was searching for one day. If your dates are flexible there will be more of a chance.

If you are willing to sit it out I still might chance it without an ADR, but be prepared to shop while my family ate.