Hi, Robyn! Welcome to the Disney Parks Moms Panel!
You've got quite the "Grand Gathering" of family members vacationing with you, what a blast you will all have together. You've also made an excellent choice in choosing Disney's Port Orleans - Riverside Resort as your home-away-from-home during your stay. I have stayed at this charming resort several times, so I am happy to help.
Disney Bus Transportation is very ECV friendly and Cast Members are more than willing to help. However, most buses can only accommodate two ECV's at a time; with a few buses for larger resorts, like Port Orleans - Riverside, accommodating up to four. As far as the best stop to use, the first one on the route would offer the best chance to get as many of your party on the bus as possible. Currently, the West Depot is served first, followed by North, East and then the South Depot before heading off to the theme parks. It might be beneficial to request rooms located near the first stop. Select the highlighted link for an
interactive resort map, including bus stops (Port Orleans - Riverside is located in the Disney Springs Area). I also suggest notating on your reservation guests that will be using ECV's. This information really helps the resort to be prepared on your arrival.
ECV guests are offered priority boarding and can bring up to five additional guests with them at that time, additional guests will need to utilize general boarding. With four out of ten in ECV's, you should all be able to be accommodated based on availability on the bus. Bus transportation is the only option available for ECV's to the theme parks without renting an ECV compatible van. For transportation to Disney Springs, you can take a bus or ferry boat.
I hope this information is helpful in your planning, Robyn! Please let me know if you should have any additional questions.
Faith