Cargo shorts are probably a good option unless the pockets aren't zippered.
I wouldn't call my choice of pants for parks cargo shorts as they don't look like the typical cargo shorts. The size is about the same but the pockets seem deeper and are on the inside rather than on the outside. Also, the pockets are at nicer spots. Most cargo shorts seem to offer pockets where restraints or seats would wrap around, resulting in pressure on phones, cards, etc.
Not sure if it's still a cargo for Americans (at least around here it's not) but I don't know any special name for them.