I am not the most knowledgeable person here, but I can tell you about the i-130 process for my wife and step-daughter who are Ukrainian and interviewed in Frankfurt. I am just not aware of any possible differences between a spouse I-130 and a parent I-130 if any.
You should only set the medical appointment after receiving the consular interview date. The visa you receive is only valid if the medical is valid, and I think it was a six month expiration date.
They will not need a translator at the embassy. The people interviewing them will speak Ukrainian and Russian.
Prior to setting an interview date for them, I reserved medical appointments in Frankfurt based on the expected interview date because the lead time for reservations was so long. Once I had an interview date, I cancelled the Frankfurt medicals because I was able to get an appointment with a Doctor in Vilnius Lithuania. The doctor himself, Richard Cervin, answered multiple emails with my questions. He confirmed no translator was needed, and translations of the vaccine records were also not needed provided they were readable. He also looked over the vaccination records because some must be taken with time intervals between them. He confirmed the remaining ones could be done the same day in his office. My point is that he was very helpful in answering questions and ensuring the medicals went without incident. His website can be found on the US Consulate page:
https://travel.state.gov/content/travel/en/us-visas/Supplements/Supplements_by_Post/VIL-Vilnius.html
http://www.clinic.lt/
My first email to him was 6/2/22 and he answered the same day. I had a Frankfurt appointment date at that time. The medicals were completed and submitted electronically on June 29, 2022. Twenty-seven days from initial contact to submitted medicals. The medical appointment was for June 27th (Monday) and he recommended they stay in Vilnius until that Friday, July 1, in case there were reactions from the vaccines. I cannot recommend this doctor enough.
As for the interview in Frankfurt, they claim that no cell phones are permitted inside, but that isn't true. We left ours at the hotel, but others were allowed in with them. Our visa appointment was July 11th and we decided to rent a car and drive to the Eagle's Nest and the Bavarian Alps while we waited for the passports to be processed. On July 13th I received an email saying their passports could be picked up on July 14th.