Celine Dion -- I'm Opening My Palace on the 4th To Lonely Airport Guy

Celine Dion is making sure Lonely Airport Guy (LAG) won't be alone for the 4th of July ... because he'll be spending the holiday in Vegas with her ... and 4,000 other fans.

Our Celine sources tell us ... she's making good on her offer to Richard Dunn ... whom she invited to her show after seeing his hilarious lip-sync video of "All By Myself."

We're told Dunn and his wife will fly to Vegas for her Independence Day show at Caesar's Palace ... and Celine has graciously agreed to put them up at the hotel at her expense.

Best part ... we're told Celine wants to meet Dunn before the show!

Dunn tells TMZ he's "pretty blown away." Luckily, his heart will go on.