Can i buy stool softeners for kids?

Safe for most kids: Docusate (per pdr) helps moisten & soften hard, dry stools. It is not true laxative, but facilitates natural defecation, usually within 12 to 72 hours. This is safe & available for children over 2, & assumes normal GI anatomy without inflammation, stenosis, extrinsic or instrinsic obstruction. Change in bowels is a "red flag", like weight loss or blood in stool, that needs evaluation if persistent.

Mirilax: Despite its name this is a product that just grabs water molecules when it is moistened that are not easily removed during digestion. As such it moistens the stool & prevents it from becoming hard. It has been my go to softener for decades.