FIRST (https://www.firstinspires.org/) is a more structured program intended to be organized through schools or similar communities (homeschooling groups, 4H, etc.). I have more experience with the bigger robots intended for high schoolers, but they have programs all the way down to kindergarten.
Doing something similar at home is very possible, and if you are nearby an existing team or program they are usually more than happy to have a conversation with parents about how to get their kids started even if it doesn't mean joining the team.
+1 for FIRST. This is your path as it is structured and can also help your child build friendships with other kids interested in robotics.
Additionally, participants who stick with the program through high school learn every aspect of robotics - problem solving, design, fabrication, testing, coding, presentation, teamwork, etc.
That is a great point, the things I value most from my time in FIRST are the friendships, connections, and soft skills I built. The engineering is fun, but I definitely use my teamwork, leadership, research, and presentation experience more on a regular basis.
Additionally to the OP, if you want this to be something that you and your kid do together, you can volunteer as a mentor for the team if your schedules align. You can have a very large impact beyond just your kid by doing so.
Doing something similar at home is very possible, and if you are nearby an existing team or program they are usually more than happy to have a conversation with parents about how to get their kids started even if it doesn't mean joining the team.