That was about where I stopped reading in your original post as well. Nyack to the Coliseum is just... honestly, if they plan on going either way anytime NEAR any rush hour (like, from 7-9:30am or from 4-6:30pm), I can't see it taking less than 2 or 2.5 hours for the one-way trip and it could conceivably be way, way more, as anyone who has ever either waited to get on the Tappan Zee, or ever driven anyplace on Long Island in daylight, ever, will tell you.
From NYC to Nyack is about an hour on a good day with no traffic. From NYC to the Coliseum is like 45 minutes - an hour on a good day.
You can cut out the middleman a bit (not go through the City itself) and go Cross Island over the Throgs Neck to the Hutch to theTappan Zee (which, btw, whatever transport they're taking, this is something like $15 in tolls each way, each time they go back or forth for each single car making the trip, buses pay more cause it's per axle) but it's still likely an hour and a half with no real traffic at all.
Around the Coliseum there's some fast food I think, off by one side... I know there's a Dunkin Donuts. There's a decent sports bar with not bad food in the hotel there but while it's not particularly expensive it's not particularly cheap either.
Oh, also be warned you CANNOT walk to anything around the Coliseum (besides the Marriott). Can not. Need a car to get to, from, to the Donuts, to anything. It's surrounded by multi-lane highways and roads and the drivers are not kidding around.
You can walk around Nyack, which has plenty of nice little restaurants (depending on where in Nyack they'll be), but not fast food really. There's the Palisades Mall but that's on its lonesome too, kind of the other side.
Honestly, I realize you're trying to save money but the geography of this makes this a really, really bad plan. Unless it was just going to Nyack, sleeping, going to the Coliseum and then going home for good, rethink.