The Franklin Institute would be my first thought. Or the Academy of Natural Sciences. Or both. The FI is showing the Hobbit and something else I can't think of off-hand in the IMAX.

I also thought of the Franklin Institute. There is a lot to see and do there.

Thanks! I will check out the FI website! Any other thoughts?

Will Longwood Gardens still be decorated? It has indoor and outdoor gardens.

They may be too old for the Please Touch Museum.

Franklin Institute.

Adventure Aquarium

Philadelphia Insectarium

Are the lights/decorations still up at Macys?

Reading Terminal Market

Air Mobility Command Center in Wilmington and then lunch at the aircraft themed restaurant.

Or drive a bit northwest and visit Hershey Park.

There are lots of food tour places like Utz, Herrs, Turkey Hill.

Way too old for please touch. My friends bring their 3 year olds there.

I hated Longwood as a kid.

There are early fireworks at 6 on the river. I'm not sure how that might impact traffic around and visitors to the aquarium.

Visit the Camden Aquarium.
At 6 pm, watch the fireworks over the river. I recommend you do this from the Philly side
www.visitphilly.com/articles/philadelphia/where-to-watch-new-years-fireworks/

If you use mass transit well, traffic will be a moot point. Ride PATCO from Center City to the Walter Rand Transit Station, then the River Line to the Aquarium. Be certain you FULLY understand all the stops and directions, as Camden is NOT a city you want to get lost in!

If you decide to go to Longwood Gardens, be sure to check online regarding advance-sale timed tickets for tomorrow. There is a terrific indoor children's garden but it's aimed at younger visitors.

I'd agree that Franklin Institute would be be the most fun for boys of their ages. But depending on their interests, the Natural Sciences museum or the University Museum might be good choices.

I've just come back from NC (went to the OBX over Christmas) and I'll agree that it will feel chilly! I'm finding it hard to get used to after just a week away.

A lot does depend on their interests/school subjects, but a combination of the Wanamaker's store (now Macy's) http://www.wanamakerorgan.com/xmas.php with the small Septa museum (great pix on the trolley!) with the Reading Terminal Market and maybe an el train ride down to the historic area worked really well for me at a similar time with kids from 2 to 18. The train ride was a highlight, actually! We also did a horse/carriage tour around; even though it was cold, it was a lot of fun for all.

The University of Pennsylvania Museum of Archaeology and Anthropology is one of my favorite places in the city (it's mentioned above) but may not have as much to hold the attention of the 2nd grader, depending on his interests.

Have a great day, and don't forget to eat like a local!