That is correct Tauck family tours are called "Bridges"
The other thing to consider when comparing is to look for the word "optional" in descriptions of the tours. A lot of companies list places you "can" see while you are there but are not necessarily included in the price. With Disney everything listed is included in your price
The last thing to compare are the hotels that are offered with the different companies
With Globus family tours in Venice you are staying at Venice Lido not Venice proper. I could be wrong on this but I would take it to mean that if you don't return with the tour to the hotel you have to pay for the vaporetto to get to the center of Venice from the Lido
Here is a photo of the map to show you where the two are from each other
Here is an example of things being options which means you have to pay extra for them
http://www.globusjourneys.com/product.aspx?content=itin&trip=7ZH
Day 7At Leisure in Venice
(Sat.) A whole day to explore Venice on your own: join the locals and ride the Vaporetto, have a cappuccino at a sidewalk café, or wander through the narrow streets and discover Rialto Bridge. To top it all, why not join
an optional cruise to the charming island of Burano, followed by dinner with local specialties to celebrate the success of your Italian vacation. (BB)
Just some things to consider and take into account when looking at the prices