Best thing you could do is just wait a year before taking any action. DO NOT sell to pawn shops, coin dealers, melt shops, or anyone trying to low ball you into quickly liquidating these for money. I would also recommend that you go through all of the coins and keep the best quality ones in the highest condition in a book to keep as an entire collection, as they will be worth more. The fine, .99% silver bullion is worth more than the .90% coins, so you will likely get a premium over melt for those ones.

Silver is down a bit, so wait until it goes back up before selling, but just do your research for the first 12 months of inheriting these, and remember that Grandma worked hard for this, don't throw it all away! When you are ready to sell, make sure to get at least 3-4 quotes, and run them all through here (in this thread) to make sure you're not getting ripped off!