Judging from my experience with Slavic languages, the following could work quite nicely, provided the translation is direct and not through English or any other "middleman" language:

1. Czech <=>Slovak (should yield good results, the two are mutually-intelligible)
2. Polish <=> Silesian (pretty much mutuall-intelligible)
3. Polish <=> Czech
4. Polish <=> Slovak
5. Polish <=> Ukrainian (vocabulary is in many cases interchangeable, but Ukrainian grammar is closer to Russian than to Western Slavic languages)
6. Polish <=> Belarusian (same limitations as in the case of PL-UK language pair)
7. Ukrainian <=> Russian
8. Ukrainian <=> Belarusian
9. Belarusian <=>Russian
10. Slovenian <=> Czech (Slovenian is the closest to Western Slavic languages)
11. Slovenian <=> Slovak
12. all Southern Slavic languages together, especially:
    1. Macedonian <=> Bulgarian (some say it's the same language)
    2. Croatian <=> Serbo-Croatian <=> Serbian

Do I add them to the Google Docs document myself?

Agree

but English -> Ukrainian is also needed

Well, most definitely English <=> all languages listed would be beneficial as English wiki has often the most referenced info even on CEE topics. But it all depends on whether such translation would actually be helpful. If it's anything near Google Translate, then I believe it's easier to copy the text and translate it by hand than to use some machine assistance.