Caution is definitely advised in immunosuppressed patients when contemplating cosmetic procedures. There is an increased risk of infection with procedures like fillers and laser resurfacing.
If Botox is reconstituted sterilely and the procedure is performed on clean and infection-free skin, and prophylactic antibiotics are given, I don't see a great problem with Botox.
As for fillers, if you recall, fillers like Sculptra were initially designed for HIV + patients, also immunosuppressed, for correcting lipoatrophy.
Consult a board certified dermatologist or plastic surgeon with training and experience in cosmetic procedures. And include your transplant doctor in the discussion. Between the three of you, you will come up with the right decision.