Travel from Lake Bled to Ljubljana Airport

Contact the hotel. They may be able to arrange a driver/taxi.

You'd probably want to take a 1 hr. bus ride down to the airport the day before.

And then catch a taxi to one of the airport hotels 2 miles or so away from the airport terminal.

Everyone on our tour leaving from Ljubljana on Sunday took a cab and had to leave at O’Dark 30. The hotel (assuming you will be at same one we were at) will arrange the cab and your tour guide will be there to help too.

Consider flying home out of Venice - and taking the Slovenian shuttle service GoOpti from Bled to Venice airport. It's under 3 hours from Bled to Venice Marco Polo Airport. You can probably take GoOpti the short distance to Ljubljana airport too, but you might get a much better flight (possibly a lot cheaper flight) home out of Venice, and it probably won't leave Venice until late morning. You'd still have to leave Bled early. Check your flight options.

FYI. Go opti does operate shuttles between Lake Bled and the airport. I saw them last fall.

I had a rental car, so I drove. BUT I found that the B&B/hotel owners were great at helping me arrange anything I needed while in Slovenia -- from a local city guide to a mountain guide to a driver. So... I agree with the person who encouraged you to ask the hotel.

If you are willing to extend the trip for a day, I would suggest catching the bus to Kranj. It's a town just a few minutes from the airport. It has a nice old town, a gorge running through the middle of town, a palace with a regional museum, and an arcade created by Plečnik (Slovenia's nation architect). France Prešeren, the national poet of Slovenia whose work is used in the Slovenian national anthem, had a law practice in Kranj toward the end of his lift, and the office has been turned into a Prešeren museum. There are tunnels under the city built by the Nazis to provide cover for the industrial workers in case of air raid (no air raid ever came). There is a great building that was renovated after Communism times. The front of the building was left in Communist form but covered with a material that purposely rusts; the back of the building is a gleaming, sleek, modern facade; my interpretation is that the building takes you from rusted, corrupt Communist times to a modern future for the town and the country. If you are a visual person, here's a YouTube video of highlights of the town: https://www.youtube.com/watch?v=8Yx8JRVVmJg

Guesthouse Stari Mayr has simple, clean rooms at a reasonable price that are located above an old town restaurant that has been in business since something like 1850. The owner of the restaurant and the rooms also has a taxi service that, at least pre-COVID, was free for guests to use (e.g., to get to the airport) -- not sure if it would be free though if you needed a really early departure. The owner was great at lining up the taxi for me and for finding a local to give me a tour of the town.

Have you looked at flights from other airports? Ljubljana airport is very small so your options will be limited.

If all you need to get going is a flight to Frankfurt to make your connection to Boston - getting to LJU is only a 30-45 minute drive away from Lake Bled. Contact your hotel in Lake Bled directly to be sure that arrangements can be made for that transfer (with RS terminating tours in Lake Bled I'm pretty sure that is a well-beaten path.) Venice really isn't a viable option.