Solobiker: If you have it done, since the kidneys are marginal, please make sure they use IV fluids while she is under. This helps to maintain blood flow to the kidneys while under anesthesia (otherwise, the gas (or other anesthesia) causes the blood pressures to drop, and the kidneys do not receive the blood they should). This can contribute / worsen kidney problems that may already be present.

If the teeth are bad, cleaning may not be the only issues... they could find some that are infected and need extraction. If this is true, getting it all taken care of can really make them feel so much better! And without any anesthesia, this simply could not be found or dealt with.

It's always hard to know the right recommendation in a geriatric pet. I even struggle with it with my own (she is 12). I'm planning to get it done soon, though.

Nothing like fresh doggy kisses that don't make your nose curl
Good Luck.