Same call, same time
The 7pm bedtime call. Same time every night. Kids handle separation much better when reunion is predictable.
The 'something for you' parcel
A small thing in the post once a week — a postcard, a sticker, a chocolate. Costs nothing, means everything.
Honest with the kids about timing
'Daddy/mummy will be home in 12 sleeps' is more useful than vague 'soon'. Kids can manage a countdown. They can't manage uncertainty.