I'm in a similar situation. All my family are overseas, I'd love for the kids to go overseas. We are actually planning to go to the UK next year (Easter) for my brothers wedding, but with the current situation I doubt we can go. Not necessarily due to not taking vaccines, but more to do with the lack of available flights back. If I can't guarantee that I can return to Australia then I won't go. Too much impact on the kids education if they can't get back to Australia, or if I leave them here and go by myself, then I run the risk of not seeing them for an unknown amount of time.
Last time my kids saw their grandparents is similar to yours. We went to the UK for Christmas 2019.