What is maximum HSA deduction in 2018 for family coverage over 55 but one member will be covered by Medicare Part A in March 2018?

I will turn 65 next March and will have to enroll in Medicare Part A. I will still be working and covered under my company's medical plan as well. What is my maximum allowable HSA contribution for family coverage in 2018 limited to $1,16.67 i.e., (6900+1000) x 2/12? Does it matters that my wife will still be under 65?"