I would take Metro North into GCT and then subway downtown. He can get one of the pre-arranged ferry slots through NYRR to Staten Island.
For you, drive but park uptown on the west side (possibly use HH Parkway). Anything on the east side will mean navigating street closures. Not sure if crosstown buses run during the street closures, so be prepared to walk. Depending on how old your kids are, you could catch your husband in multiple spots, i.e. headed north on First Ave around the 18 mile mark and then south on Fifth Ave around 23 miles. You could walk between the two before he would get around. Believe me, having family or friends cheering you on at those spots is huge for someone running a marathon.
Central Park finish will be jammers - so unless you get their early and wait around for hours, forget it. Arrange to meet your husband somewhere close to the finish but away from the park, Broadway & 70th for example. If you've seen him come down Fifth Ave around mile 23, you can walk through the park and meet him on the other side. It's going to take him some time to get through the finish area, grab his gear bag and make it to your meeting point.
The maps for the course and finish area will help you find good locations:
Race Day | TCS New York City Marathon