Has anyone in the party been to Disney?
If so, they would be a natural lead, if not I would find out what everyone's expectations are for the trip and make sure they take some responsibility for their own vacation. If you can get everyone together for a planning dinner - maybe adults only that's a good start. What parks do they want to visit, must do attractions, character greetings (this could be parlayed into a meal if lots of kids like the same character). What's everyone's meal budget and preferences, early dinner vs late lunch, sit down vs quick serve.
With essentially 4 families I would have at least 2 if not 3 rental cars or plan to use rideshare.
It's been said upthread but be willing to split up - early risers vs night owls. We have done trips with extended family and that was the key. Some days we left together and split after lunch, other days we met at lunch and stayed together for a few hours. We usually stay onsite but not all together, depending on each family's budget and it works for us.
You asked about travel time - to be realistic - air BnB 20 minutes from Disney means at least 45 minutes to an hour travel time once you add in traffic and then actually getting to the park, esp. MK where you will also need to take a boat or monorail. Once onsite travel between parks can take an hour or more, not sure if that's what you meant,
I would suggest watching some you tube videos to get a better idea of what is offered at each park, "All Ears" has some great ones as does "Mammoth Club".
Don't try and do it all, focus on a few must do's from each family member and take it from there. If you miss something that's just a chance to return in the future