Nasolabial fold filler. Would it make my smile look weird? (Photo)

There are new fillers that provide subtle, natural volume and are more spreadable.  This way the doctor can smooth out the product to exactly where you need it.
Juvéderm Vollure XC is an example for nasal labial folds (those deepening parentheses lines around your mouth).  Vollure lasts up to 18 months and the great news is that re-treatment requires 1/3 less product!  
Restylane now offers two next generation fillers that also provide a more natural look:  Defyne and Refyne move with the expressions of your face, so you don’t look puffy or stiff.  They have been in use in Europe since 2010.  Restylane Refyne has more flexibility and less support to help with moderate wrinkles, such as those around your mouth.When you're contemplating cosmetic treatments on your face, the qualifications and competency of the injector, as well as the safety of the product, are very serious considerations.  Your injector should be a board certified physician with the American Academy of Dermatology or with the American Society of Plastic Surgeons.  A board certified doctor is trained on the anatomy of the face to avoid complications and undesirable (or even disfiguring) side effects. 
To answer your questions about a “tube” of product—each syringe holds 1 ml.  To give you a visual, there are 5 ml’s in a teaspoon.  I often use the analogy 5 cc or 5 ml or 5 syringes will fill a teaspoon.

Hi
You have a wonderful smile and doing some filler in the NL folds well should only keep the focus on this great feature.
I think one syringe to start should be good. Depending on your wallet and desire to do things you could do some midnface filler but that may not be necessary yet.  There is some asymmetry to your NL folds (which is quite common) and this can be helped with a good treatment 
Good luck and keep on smiling!