Apps are useful, but a sheet of paper on the fridge is something the whole household can see at a glance.
Draw seven columns on Sunday evening. Write the fixed things first: work, school, appointments. Then add one or two things you want to make time for, like a call to a friend or an evening with no plans at all.
Keep it rough. Cross things out, move them, add notes in the margin. The plan is there to help you, not to judge you.
At the end of the week, look back for a minute before you throw it away. It is a good way to notice what actually filled your days.