hey hey Laura
i really have no idea about taxis available in the area and may be rare and expensive with wait times.
we were 4 long times friends from san francisco bay area (say hello) and was one of my things to do. found oriana, a private van tour through the prosecco region about 5 to 6 years ago.
orianancc.it
she was fabulous, speaks great english, born, raised & lives in area. great communication with emails. i think we did a 5 hour tour.
we were staying in venice, took the train to susegana and she met us right on time at small station and away we went. drove through the gorgeous green hills, small villages, stops at couple wineries with lots of tasting. we wanted local prosecco, not what we can get here, stops at photo op places, stopped at a small family restaurant for lunch, her choosing. different homemade dishes brought to table to share plus prosecco. bought some bottles back to venice for our happy hour at apartment patio.
if everyone mobile (walking issues), ask her about the vending machine up a short walking trail. 2 of our group walked up to it, took small euros (coins/bills, credit card?), took picture with the pretty views, bought bottle out of machine, heard they have "chacuterie goodies". the girls came back laughing so much having fun.
my own opinion, i would not want to drive, leave it to a local. plus you will need to get an IDP (mandatory in italy) a car, read the laws and rules about renting, rules/laws, parking. this is one of my favorite tours with all the trips to europe.
if you're staying in venice, another fun thing to check out
schezzini.it
alessandro does a "cichetti" bar crawl. stopping a a few bars with small type appetizers, tasting wine and history of venice.
email him for more info on his page.
friends of ours took the short train ride to treviso from venice and loved it. small town with canals, piazzas, of course had their world known tiramisu and a dish with radicchio away from crowds. have fun & enjoy. if you do the tour please post back
aloha