Help make my sons dream come true!

I'm heading to NY with my kids tomorrow and I can't find any information online anywhere.

My son loves trains of all types and one of his wishes is to take a ride on a double decker train. Since we don't have much time, I remembered seeing that the LIRR has some double decker trains - but I cannot find any information about what routes they are on.

Does anyone have any insight on their routes and schedules or are they assigned randomly? The closest station to us is going to be Hicksville and hope that there are some double decker trains who can catch from here's (either direction).

I'll call the LIRR helpline tomorrow but am hoping the good folks of FT can help.. Thank you.