According to my calculation your pan is slightly larger than an 8-inch round pan. You would need to bake quite a few of those cakes to feed 60 - at least four of them (three layers each). Maybe consider a sheet pan instead since it feeds larger crowds. Having to frost and decorate a bunch of smaller cakes separately is more time consuming than doing just one large cake.
Ganache is great underneath fondant - some prefer it over frosting because it smooths very well.
People prefer different fondants...I personally make homemade marshmallow fondant. It's much cheaper than store bought and surprisingly easy to make. Just google for recipes - Elizabeth Marek has a great one with a youtube tutorial. Whatever you do don't use Wilton fondant - no one likes it. It's dry and tastes bad. Ironically, Elizabeth Marek's recipe does add a little Wilton fondant to her homemade recipe for structure. There are other marshmallow fondant recipes out there. If you want to buy it some brands I see recommended here are Satin Ice, Fondx, and Fondarific. Here's a chart on how much fondant you might need. I would buy/make more than necessary because fondant can be wrapped and kept for months.
Definitely bake your cakes and freeze them a week ahead of time. I do this with a lot of big cake projects. Freezing will actually make your cakes moister and it's easier to handle a chilled cake (less likely to fall apart). Once your baked cakes are completely cool wrap them in a good quality plastic wrap (all brands are not equal) and then in a layer of tin foil. You want to protect the cakes from frost and any scents possibly in your frig/freezer. Make sure you wrap them completely - cakes are like sponges and will absorb whatever is around it. I usually double wrap mine. The morning before the party remove them from the freezer and defrost for an hour.