Wow, surprised at some of these replies. I don't think OP is saying their 10.5 year old kid wants to start doing 200 lb squats or dead lifts.
Our 11 year old started doing some casual strength training last year to help with some of his sports interests (swim strokes for example). The weights he uses are not significant and he learned proper form first. Some weeks he does it 3-4 times, some weeks not at all. I wouldn't discourage it, I would support it - but make sure he learns proper technique and focuses on more reps and less on heavy weights.
Here's an article on the topic, but YMMV
https://www.verywellfit.com/a-weight-training-workout-for-children-3498516
Here's an excerpt that I am sure will send some of you off a cliff...
"Optimal Age to Begin Strength Training
Weight training is appropriate once a child can maintain balance and postural control and can listen to and follow directions.
This is usually around age 7 or 8 but it depends on your child's maturity level.
Although children under 10 years may develop strength from training with weights, adolescents ranging in age from 10 to 15 are usually the group most interested. Your child should also be eager to train and be prepared to train multiple times per week.
Strength training for kids is not weightlifting, powerlifting, or bodybuilding in their purest forms, which are aimed at competition. These distinctions should be clear to parents, trainers, and children."