Hi Gretta,
I apologise if I won't be answering your question because unfortunately, I don't know the answer. I have this reply, 'cause when I read your status - you have a husband who is an EEA national and you hold a Residence Card of a family member of an EEA national, I suddenly thought that maybe you could help me..
My fiancé is an EEA national living here in the UK for over a decade and my entry visa here is an EEA family permit (fiancée) which is valid for 6 months only. We are getting married soon and I don't know my next step. I received 2 different answers from my post and I'm still making an investigation. Yet, I still don't have a valid answer.
Anyway, I hope your parents will be given a chance to travel here in the uk.
Sorry if my reply is off-topic.
Adhing