Places vs. Listings and Select all button for the map

Hello, I am working on the website http://www.denverlocaleverything.com and am looking to add a “select all” check box to the top of the list of all the place categories on the map showing on my homepage. I would like visitors to be able to click this and have all the categories selected at once, or deselected at once. Is this possible? If so, can you please guide me in the right direction?

I am also looking to have a full list of all the places that have been posted to the site show when I click the button “Directory” on the secondary menu. I assumed all the places would show up when @ the URL http://www.denverlocaleverything.com/listing but this only shows 2 pages of listings and I have many more places.