I find Rube Goldberg machines to be fascinating and fun and this one is quite impressive and timely. Creating a simple Rube Goldberg machine, using toys or other household items, can be a great challenge for kids.
Similarly, creating a 3-D kinetic sculpture can be done with things you have at home and can be quite fun. It can be done in a little time or be a project to which your child dedicates a good period, depending on their interest.
If you are trying to get your child to do more writing, creating a mini-book might be a good option. This short video shows how to create one.