Jeff Bezos & Lauren Sanchez's Wedding Island Partially Open to Tourists

Jeff Bezos and Lauren Sanchez can't buy everything in the world with Amazon money, it turns out ... 'cause the island they're getting married on isn't closed completely!

Sources with direct knowledge tell TMZ ... businesses on one side of the island of San Giorgio Maggiore -- including two museums, the sailing club and a café -- are open all day and will close at normal times, and the side of the island they're on won't be shut down for the event.

However, the islet is set into two pretty distinct parts ... with one half covered by businesses and the other dominated by the wedding grounds and the Teatro Verde amphitheater, as well as sprawling greenery. It's unclear whether the Basilica itself -- where the couple is reportedly going to take their vows Friday -- is open to the public during the daytime.

We're told guests are going to stay on that side of the island ... and will most likely arrive at the side with the church and amphitheater on it instead of walking through the other side.

Our sources say there's a simple reason Sanchezos can't shut the whole place down ... the island isn't available to totally rent out -- no matter where you rank on Forbes' World's Billionaires List.

The wedding ceremony is expected to take place soon ... unclear if guests will have their phones or if they have to surrender them like they've been doing.

The weather looks good on the small island -- which is about 25 acres in total size -- with lots of sunshine, as Lauren arrived in a stylish white dress earlier today ... and, a repeat of last night's torrential downpour is not expected.