I would make a starter yes. Making a starter is almost always better than not making one. To make a starter, combine two cups of water with 1/2 cup of DME. Bring to a boil and allow to boil for approximately 10 minutes. Then cool. Once you reach pitching temps, add your vial of WL yeast and shake thoroughly. You will also want to swirl the container regularly. Obviously sanitation is very important too. If you are planning on using it on Sunday, you will probably be pitching at the perfect time. Usually 2-3 days before pitching is best. You will be fine. I have even made a starter in the morning and pitched it in the afternoon with results better than just pitching the vial.