The best way to do this is to add a link to you the Registration Confirmation email your registrants receive automatically.
To add this link go to your event and click "Registration" on the navigation menu. Click "Settings" in the upper right corner to go to the Manage Registration Form.
Copy a link to the hotel you would like to recommend in the "Hotel Booking Link" section. Once registered, your guests will automatically receive a confirmation email, if your link is included on this page, the email will have a "Register For Your Hotel" button, taking them to the webpage you linked on this form.