Stay analog and cheap!! My 12 yo has lost three!! The 8 yo I think will be a little more serious about wearing and holding onto one, funny how different these little creatures can be!!>)
I got my first watch when I was 10, it was a Star Wars model with a red LED display. It lasted all of 3 months, I found out the hard way that it wasn't waterproof when giving the dog a bath.
Start with something durable, but inexpensive. You can get him a good watch when he graduates high school, or an even better one when he graduates from university.
How about 2 watches? A beater for school & play and one for dressing up. I have a Bulova and a Seamaster from the '60's yet, unless I'm dressed up to go someplace special, I wear a Casio Forrester ($20 at Walmart with a velcro band). I've scratched or cracked too many crystals to wear my good watches every day. The Casio, and the Timex Expedition before it, have taken a pretty good beating.
I'm into vintage mechanical watches; they require periodic maintenance & are generally not as accurate as the quartz models. However both my kids (son 22 daughter 19) wear watches I've handed down to them. They become heirlooms with a story and special meaning. In the past, it was rare for a watch to measure more than 35mm so finding a size for a 10 year old is easy. I've up-graded the kids watches as they got older but both still cherish their first watch. From a reliability standpoint, a self-wind watch may be better. I admit it's easy for me as I have dozens of watches I've been collecting since I was a teen 40 years ago. I think a great starter watch would be a Hamilton Military watch or one of their rectangular models; either can be had for <$100.