Thank you for the response, lo2e. Yes, I've heard many good things about the Wellington station, and sounds like you confirmed it too.
Here's more detail. I've parked at Alewife before, and it's perfectly fine. But a couple of things that annoy me are (1) they warn that you can only park there 7 days or less and (2) sometimes finding a space is a challenge, even though the parking garage is humongous.
Since Wellington and Wonderland station parking lots are smaller (as far as I know), my first concern was space and availability.
Also, I heard that for overnight parking at Wonderland, you have to prepay with attendant collecting money as you enter. Is this still true? Obviously, this could be a problem if your plans change.
I just want to compare the options, and see if anyone has any experience and share whatever he/she can.