How close can you get to the sun?

You can not get very close, without a heat shield. As soon as you passed Venus the shield would get so hot it would melt as the temperature would rise into the thousands of degrees. as soon as you peeked over that shield this is what would happen.

We are booking our hotel stay on the moon next week

Have you booked your stay at the Moon Hotel ? I will get you started . First you will need to go to your doctor and get your physical to make sure you are fit enough to travel to the moon. You will experience some high amount of G-force as you ascent into space. Your total cost for this flight and hotel stay will be 2.3 million dollars, US.

What will happen to the earth in the future

The sun will grow larger and larger over the course of millions of years and hopefully by then mankind should have been able to terraform other planets in our solar system farther from the sun and take most of the earths lifeforms there or travel to the nearest stars to colonize other planets. By then the oceans on earth will likely disappear along with all other life forms.