Lightweight boy pants

My son does not like shorts. I'm trying to figure out lightweight cotton pants that I can buy online, but when I search Amazon or other sites, it's hard to figure out the material. A lot of things seem to be thick/fleece ​without clearly saying it.

Does anyone have specific boy pants they like? 4-5T or 4-5 kids.

Also, wrong subreddit, but, on the other hand, my daughter needs similar pants but she's way bigger, so she needs a bigger size, like 10, but way shorter. If anyone with an other kid has suggestions...boy pants are fine. Or capris? ​