We sailed on Princess last May/June ending in Venice. We stayed at the Hotel Olimpia, located close to where the buses or taxis drop you off from the ship. It does involve a little walk, only because you have to cross a couple of bridges to get to the hotel. Since your wife is pregnant, you might have to make a couple of trips with luggage. Here is the link to their website.
Hotel in Venice Hotel Olimpia Venice | Official Site | 3 star hotel Piazzale Roma Venice