Eating olives and avocados as part of an overall balanced diet should be safe. I am not a dietitian. Dietary advice should be given in the context of a total diet. Olives and avocados would be high in potassium and this needs to be factored into your diet. As long as you monitor your kidney function and your blood potassium on a regular basis and consider all dietary preferences in moderation, these choices should be safe. This should be discussed with your physician and dietitian.
For additional information about nutrition and early kidney disease, please visit: https://www.kidney.org/atoz/content/nutrikidfail_stage1-4