Without a spouse, how do I keep up a family routine of worship for the children?

One parent is enough to bring a home to life with worship; you do not need a spouse for that. Set a fixed time for praying in congregation with the children, even if you lead, for daughters or young sons. Read the Qur'an and short supplications together before bed. Keep it relaxed and consistent, not a burden that adds to your tiredness. Invite older children to take turns leading the recitation so they feel involved. Pray for your children by name and teach them to pray for their late parent or for their parents. A small routine that continues plants deep roots of faith. See du'a & prayer.