This was actually an issue for our application as well - or at least the specific objection was that the notary would not witness signing of a foreign language document. I suspect it's the same issue in Ukraine.
We did as you did, had the form translated into Russian, had that form signed by the non-accompanying parent and witnessed by the notary, and then translated back into English (with notarised translation). I didn't like that much because the format inevitably changed and the legal language in Russian, although certified by notary/translator, well, you never know what specific legal language they wish to see. I did, however, ask the translators to at least try to conform the English-language final to the original form's language (although I didn't check word for word after, it looked close). I put an explanatory note attached from me that we did it this way because notaries would not witness foreign language docs.
Just after we got that signed and translated, I got from a contact at the Canadian Embassy a dual-language version of the form, English and Russian - I guess on basis that a notary could witness a dual-language version. I chose not to re-execute because dealing with the other parent is not always easy.
At any rate, my application was not returned so I guess they found it to be acceptable.
So: you could do as I did, or try to find a dual-language version through the Embassy in Kyiv (or some other solution). Not always easy to get through to the right person and depends on how accessible they are - I was lucky I had a contact but it still took a while to track this document down (too long in fact to use it).