Radio buttons will be the most clear, as far as indicating that the options are mutually exclusive. Your Option 2 check box is very unclear. It looks like you can do a search with or without promotions, but from your description you're either searching for reservations or promotions. 

I suggest something more like this: 

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![mockup showing section with 'Choose Results Type' radio buttons before search button](https://i.sstatic.net/Oqizo.png)

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