Last minute NYC question (this weekend 4/22-4/25)

We made vacation plans for a long weekend and according to the weather
reports it will be really sucky in NYC all this weekend while we are
there. :-(

Obviously, if you're gonna be vacationing somewhere, it's better to be
in a place like New York where there are plenty of indoor things to do.
I pre-ordered tickets for the ferry to Ellis Island/Statue of Liberty
and tickets for the Empire State Building but if there is an 80-100%
chance of heavy rain and thunderstorms (not to mention it being about
50 degrees) I'm not sure we're still gonna do the outdoor things, or at
least not get off the boat at the Statue. So... we're gonna be visiting
a lot of museums and sticking to the subways, rather than walking and
visiting parks.

Saturday I'd like to do the following:

- Ellis Island
- Visit Ground Zero
- Walk a few streets in the Village if the weather isn't too lousy
- TriBeCa film festival - maybe see a movie?

Sunday:

- Museum of Natural History (loved this place when I was a little kid
30 years ago, haven't been there since)
- See the Dakota and visit Strawberry Fields
- Metropolitan Museum of Art (never been)
*or*
- Guggenheim (never been)
- Visit Grand Central (probably ho-hum for New Yorkers, fascinating for
out of towners like me), step inside the Chrysler Building and look at
the murals, walk down to the UN
- Fart around Times Square, see if we can get cheap tickets for a show
that night

Is this reasonable? Too much, particularly on Sunday? We'll also have
Monday morning open - perhaps we'll do the Empire State Building then
if the weather cooperates. Any advice would be appreciated. Thanks!