Don't feel obligated to hold any events beyond the wedding itself. If you can afford to add a welcome party or a farewell gathering and want to do it, go for it. These don't have to be expensive catered events, either. You could have folks meet up for a casual "drink around the World at EPCOT" event or Dole Whips at the Polynesian or bowling at Splitsville or a barbrcue at a vacation home.
But don't forget that this is a vacation for your guests, too, and they may not want to have every minute of the trip filled with events.
As for transportation, if your events are not inside a theme park, you aren't required to provide transportation by Disney. But if your guests are not Disney experts, it can be a nice thing to do. If you pay for an hourly charter, it can go around to all five resorts, but that means some guests will be on the bus for a long time. You might want to send multiple smaller forms of transportation out to smaller numbers of resorts. Page 147 of the Fairytale Weddings Guide lists all the different types of private transportation and their prices.
Guests who are staying off-site can make their own way to the Wedding Pavilion parking lot to meet your transportation.
