My knowledge is a little out of date, but here goes...
I would put better than even money that there will be a Combat Air Patrol over Camp David during this time - typically Huntress uses 260.9, and you can usually hear the pilots coming and going out from that area on the military ARTCC freqs, along with discretes that folks usually find on the milair Sticky Thread in this forum.
In addition, there are a couple ARTCC freqs which are 'reserved' for this purpose - they are/were referred to as 'Guard Dog' - 135.525 and 126.55 (alt) along with 350.25. Note that the 135 mhz freq is occasionally used by Falls Church ARTCC for overflow or backup purposes (heard that just the other day, in fact)...
We have a quick list here, but it's, I suspect, a little out of date (Willow Grove has been closed down, I believe), but the main airports, SFRA and Andrews are all still good...
Delmarva Milcom Quick List - The RadioReference Wiki
It's a good place to start, but remember, watch that Sticky Thread - that's where you're going to find the discretes, that is if you don't hear them first...
Mike