I've been asked to approve a bronze plaque reading "Capital improvements and renovation to this organ were made possible by...." The organ builders objected that "renovation to" is a barbarism. It seems to me that part of the problem is trying to use one preposition with two nouns, but in this case I'm not sure that the preposition works well with either of them.
Perfectly reasonable to make 'capital improvements to' something or to make 'renovation' to, which appears to be the sense here. However, 'renovation of' may be a more usual pattern. What about omitting 'to this organ'? If the plaque is stuck to the organ then it would seem unnecessary to mention 'to the organ' as it would still be clear what had been improved and renovated.
I believe the correct phrasing is, "Captial improvements to and renovations of this organ" etc. Admittedly that sounds a bit stilted. The only alternative I see is serious rewording.
You proably do want to be careful about wording on a plaque because it's liable to be there for many many years. It's bad enough to make a mistake in speech and have people laugh at you. Do it on a plaque and people could be laughing at you for decades. :-)
My first thought was the organ builders should stick to their own business and stop worrying about the minutiae of grammar, but I must admit they do have a point.
The problem in OP's context is that "to" is the standard preposition to follow capital improvements, but renovation would normally be followed by "of". Two standard ways to deal with this are...
Explicitly write both ("capital improvements to and renovation of").
Omit the first preposition ("capital improvements and renovation of").
Personally, I think the first option seems wordy/pedantic/punctilious here, so I'd favour the second. But I'd also suggest singular improvement for consistency with renovation.