Bologna

You could. Luggage can be left at a Deposito Bagagli. Use Google Image to do a search on Bologna sights to see if you'd like to see them. Padua and Ferrara are also interesting.

There are high speed trains from Venice to Florence via Bologna. There are also Regionale trains but the Regionale is a bad choice between Florence and Bologna. The Freccia and an occasional InterCity take 37 minutes, non-stop. The Regionale between Bologna and Florence runs hourly but takes over 2 hours including a long layover in Prato.

So it sounds like I need to go straight to Florence from Venice (no stop in Bologna)? And I should look at reserving a high speed train from Venice to Florence.

It could be done, just as Roberto says. Your question is should you do it, isn't it? I see that you only have 2 nights in Venice, the most sublime, the most serene, the most fantastic, the most wonderful. That means only one full day. Do I take it that this is a return trip to Venice and you are just stopping in for a short return visit to see favourite places? If not, and if perhaps it is your first visit and, perhaps you will have just landed after a transatlantic flight, with jetlag - - - I'd suggest staying in Venice as long as is comfortable on your second day. Leave your bags at your hotel and just chill in Venice; really see what you can do. Bologna, only just over half an hour from Florence by train, does have the two towers and some neat stuff. I just spent 6 nights there and while I did get around to much of what Bologna offers I mostly used it as a base for day trips - to, amongst others, Florence. Venice, Florence, and Rome (I see you only have one full day there too) are the premier league. Bologna, while undeniably worth seeing and unique, is certainly in the minor leagues until you have had your fill of the big guys. Just my opinion, of course. Your preferences may be completely different than mine.

Thank you for the informative replies. We do land in Venice around 2:00 p.m. so our time will be limited there for two nights. It does sound like a great idea to just spend as much time as possible in Venice on Day 2.

I agree with Nigel. Extend your time in Venice as much as you can, and take a Freccia fast train to Florence.

Is the price much higher riding on the fast train versus the regional train from Venice to Florence? I do not plan on purchasing a Euro Rail Pass for my trip.

You are right not to buy a pass. You can compare prices for Freccia and Regionale trains by going to Trenitalia.com and looking at dates not more than one week in advance; use the tab for "Tutti i treni" rather than the Freccia default. Regionale trains are only listed one week ahead, but the fares don't vary much from week to week. The fares/schedules for after June 8 may not be available yet, but there may be discounts on the Freccie if you buy in advance and are okay with a no refund-no exchange ticket.

RE Bologna, if you have a reason for seeing it, you certainly can. If you're just stopping because you've heard of it and it's "on the way," I agree you should focus your time elsewhere. RE trains, fares on the regional trains don't change, but fares on the fast trains are low if bought online in advance (before the discounts sell out) and high at the last minute. However, similar to the Bologna question, your time is worth something too - particularly on such a short trip. If a regional train is only an extra 20 minutes, fine. But if it's an extra 2 hours, I think it's a false economy to "save" money this way - particularly since in Italy, even the "base" (full) fare isn't too high. Going to and from the Cinque Terre, you have to take regional trains at least part of the way. From Venice to Florence, take the fast train. Here's a detailed description of how to buy tickets in advance: http://www.roninrome.com/transportation/booking-online-using-the-trenitalia-website-updated