I'm not sure what the length of the gondola's are, but Disney's rules for strollers is that families load single strollers with children riding in them by simply rolling the stroller into the cabin (just as guests can do on the Monorail). Stroller size is limited to 30″ by 48″ when unfolded. Families with larger strollers are able to fold them to bring them onto the Skyliner gondolas, but the maximum capacity will change to from 10 to 6 guests. Children seated in strollers do count as passengers. So if you have one child in a single stroller or two children in a double stroller, you’ll only be able to load 5 and 4 other passengers respectively. If you are a family of over six with one or more strollers, you will be asked to board two gondolas. As with many things at WDW, you may run into the discretion of individual CM's.