Assuming you are always a good candidate to be a good kidney donor, I do not see why undergoing tummy tuck surgery would prevent you from doing so. Best to discuss this with a nephrologist and/or transplant surgeon for definitive advice. Best wishes.
It would be advised not only seek a board certified plastic surgeon for a consultation, but also a nephrologist to discuss your options. Having a consultation to discuss overall health is important for both procedures. I wish you the best Dr. Gabbay