So much choice! And it depends how far south you want to go. There would be a lot of pleasant places to see without going far -
Padova (but quite big, or you could day trip from Venice), Chioggia, Comacchio and the surrounding area and Abbazia di Pomposa
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Ferrara
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Ravenna....
A few I was going to suggest as well.
I've not been to Comacchio, but feel like it's just the sort of quirky, somewhat off the beaten track places I like in Italy. It's criss-crossed by canals like Venice, but without the mass tourism. I also recall there was a strong love of eating eels there.
Ferrara remains off the mass tourist trail, but is an absolute joy. The car would be mostly parked up here, as cars are excluded from much of the city, leaving it to pedestrians and cyclists. Plenty of historic buildings, including Copernicus' drinking place, near complete city walls and a fine castle with moat (and huge carp in it). Evening passeggiata often takes a linear route along the pedestrianised street that heads in opposite directions out of the city, plus the central squares. The weekly market in the centre of the city is excellent.
Ravenna surprised. I thought it would be more touristy, but no, there are a multitude of sites special to Ravenna, that attract tourists, but the rest of the city seemed pleasingly normal.
Elsewhere in Emilia-Romagna there are plenty of options, with coast/beach, motorsports, food, drink, history. I'll throw in a curveball suggestion of San Patrignano, who I believe do accept visits. It's a unique social project, taking in those with drug problems, but who wish to change that. They're looked after not just medically, mentally, but also in developing skills that are useful in the outside world. I recall one video where one of their cheesemakers explained how an obsessive behaviour pushed him towards drugs, but how the opportunity to obsess about cheese making turned a big negative into a huge positive. I first came across them via their wines, in particular a sangiovese based wine called Avi. Well worth a try if you see it, and I'll also recommend their Cabernet-Sauvignon led wine Montepirolo.
p.s. back up near Venice, we very much enjoyed our stay in Mezzane di Sotto, about 30 mins ENE of Verona. The place we stayed at was Massimago, who grow their own grapes and make wine (Valpolicella, Amarone and a few others). Decent but slightly small apartments (there may be bigger ones there), but with a lovely swimming pool, sauna, superb grounds and an exceptionally good & substantial breakfast delivered to your door, to eat inside or on you patio.