"You could drive to White Plains and park the car there, taking the Metro North train to Grand Central Terminal. R/T Peak fares are $18 and change and off peak are just under $14/RT. Friday, you could be on a peak train. That's also for the web ticket, which is the best price available, seconded by the station machines. It's much more expensive to buy a ticket on the train."
Here's what we ended up doing! It was relatively cheap, we didn't hit any traffic, there were no tolls, and we got there pretty quick! I would strongly recommend this route to future travelers!