what card should i open next?

My family is moving to the UK this summer for the next three years and I am wondering what card I should open next to maximize my points redemption opportunities. I currently have the Capital One Venture X and my wife has the Chase Sapphire Reserve. I presume a large part of our travel will be on British Airways, though not necessarily. Is there a UK card that we should look into or are US cards still the best bet? Appreciate any tips and advice. We are a family of four.