2 Days in St Petersburg, Russia....Ideas?

[osteome]

So a little off topic, but we have a worldly forum.

My family of four will be doing a port call for two days in St. Petersburg this summer. We are locked into doing a shore excursion due to the hassles of arranging visas on our own.

The bottom line is that given the two day window, we need can only do two of the three "must see sites".

- Peterhof Palace
- Hermitage
- Catherine's Palace

We would love to do all three, but only two are possible within the time limit.

Any recommendations?