You can't go on either the Cross County or the Hutch with a trailer. To get to Pelham Manor from the Tappan Zee, take the Cross Westchester Expressway (I-287) to I-95 South. You can get off at Exit 15 in New Rochelle and take Boston Post Road (US 1) south directly into Pelham Manor.
You might run into a problem in Pelham Manor though. It's been quite a few years since I lived up there, but IIRC most of the streets are narrow and tree-lined. Overhead obstacles (trees, power and phone lines) might not allow you to get to your friend's house. I also don't recall any place around there where it would be safe to park and leave your trailer for the night. You might want to look for a Plan B, just in case.
Good luck and safe travels!!!
