we are flying into venice staying two days we have two days in between before we go to florence for 4 days (visit daughter study abroad) where to go for 2 nights in between
Stay in Venice and take a day trip out to Murano and Burano.
I'd also suggest Verona as a good stop for two days. There's a lot to see there but if your trip is taking place in July or August, that's "opera season" so lodgings will be expensive and the place will be crowded.
You could also consider other areas in the Veneto, such as Padua. If you want something a bit different, you might consider Lago di Como (Varenna). It's about an hour north of Milan, and the travel time to Florence is reasonable.
Finally, you could add the extra two days to your time in Florence and perhaps add a day trip to Siena in there.
Verona is a great smaller Italian city to spend a couple of nights in--it's a 90 minute train ride from Venice. Then, Florence is a 3 hour train trip from Verona. Hotel Torcolo is a nice hotel in a good location...Rick's Italy book lays out a fun self-guided walking tour of Verona.
I would stay in Venice for 4 days, but that's because I think it's one of the most beautiful places on earth. Your first day in Venice will be kind of iffy, due to jet lag.