hi grieve
what are your dates for hotel in venice and hotel in florence? are you looking for two hotel rooms, double beds and what is mid-range? after cruise you will take train to florence and do you want to stay within city center? are the two couples arriving together at marco polo airport? you can reserve a water taxi for about 110E (we split cost) or get a vaporetto or a bus from the airport, others will tell you how, it's less expensive. albergo marin or ca burcia hotels, across from train station and near grand canal down alley. the grand canal is very busy and noisy. we stayed next alleyway down and loved the area. away from crowds but few minutes walk and find all kinda ways to get lost (on adventure), wear comfy shoes. and enjoy yourselves walking the island.
aloha
PS look at pictures carefully, bathroom in room and not down hall, what floor and how many steps climbing up, checkin early or drop off bags without pushing around uneven walkways and bridges, (you should be okay with midday), some have free breakfast, read fine print, security/cleaning deposit.