Topmarks games has an interactive mental maths game called 'Daily 10', you can set the level that your child is working at and then they can complete the questions given to them. It may be a useful activity to introduce to your daily routine.
Khan academy offers courses that allow children to practice at their own pace, first filling in gaps in their understanding and then accelerating their learning. They offer courses in maths, but also arts and humanities. It is American, so the grade would be different to your child's current year.
Don't forget about TTRS! We have also updated our subscription to include Numbots, which is more suited to Key Stage 1 children. Both can be accessed by logging in using the usual password and username.
I see maths is an incredible resource that offers many different activities and resources to support the mastery curriculum. In addition, they are also adding a maths lesson a day for Y3/4 and Y5/6. We would highly recommend this as an additional tool to support mathematics lessons at home.
If you would like access to mathematics tasks that aim to develop reasoning and problem solving, Nrich offers a wide range of activities for children from EYFS up to Key Stage 4.