Gday linked ...
Firstly, depending on where you're staying north of Milan I would expect there are great ski areas much closer than the Dolomites.
From Ortisei it's quite a trip to get to La Villa, and a bit of a criss cross use of various areas. You'll lift up to Seceda, ski down to the funicular (that's a great run), take the train down to Santa Cristina, a short walk to the gondola station, two lifts to the top of Ciampinoi, turn around and ski back down to Val Gardena, walk across the road bridge, short little lift, ski down to the Dantercepies gondola, long gondola up to the Passo Gardena, long shallow schuss down to Colfosco, horizontal Borest lift to get to Corvara, walk across town to the Col Alt gondola on the other side of Corvara, lift up into the Alta Badia hills. Then you have to ski over Alta Badia to get to the Gran Risa run which takes you down to La Villa - either the black run or the red run - the black one is the World Cup GS course which is an iconic run. You can continue on further up the valley towards Badia / Pedraces but it will depend on how you're travelling, and how important lunch is to your wellbeing, as to whether it's worthwhile. It's a long way back from there.
Here's an early morning view from the top of Seceda with Val Gardena in the sunlit valley below.
From Ortisei it's also a decent day trip to get to Arabba and back - probably completing the Sella Ronda along the way. Heading further afield to ski the Marmolada might be possible although I wouldn't want to swear that's true. You'd need to hit first lifts [edit - in fact you'd be better off hopping the first morning bus to Val Gardena to save time] the whole group would need to be skiing quite fast and you're not going to be stopping for any length of time along the way. That's a very long day, and (I expect) not a destination that gets recommended when you're staying in Ortisei. At least it's an easy bus ride back to Ortisei from Val Gardena if you get stranded on the way back. In fact that's probably a better plan.