Hi Diane,
Thanks for visiting the Disney Parks Moms Panel with your question. How nice of your parents to let you use their Disney Vacation Club vacation points!
Unfortunately, you will not be able to visit the Top of the World Lounge at Bay Lake Tower at Disney's Contemporary Resort. This is a perk available only to Disney Vacation Club members and those traveling with Disney Vacation Club members. From what I understand in your question, your parents are Disney Vacation Club members but you are not, and your parents are not traveling with you. Therefore you will not have access to Top of the World Lounge.
There are some other great vantage points from which to see Wishes Nighttime Spectacular from outside of Magic Kingdom. You could make a reservation at
California Grill, located atop Disney's Contemporary Resort, for dinner and head out onto one of the observation decks to see the show. This is close to the same view you would have from Top of the World Lounge. Another possibility is to dine at
Narcoossee's at Disney's Grand Floridian Resort & Spa. My husband and I dined there recently, and I really liked the view of the fireworks from the porch there.
I hope that this information is helpful for you, Diane. Have a great time planning your vacation, and please do not hesitate to ask if you have any further questions.