I agree with this, could also be tick larva (really young ticks, they go through a multihost lifecycle). If you're finding a bunch of those extra tiny ones, I suspect you walked through a nest and picked them up (good news is I believe that nymphs are less likely to carry any diseases (key term is less)). Good luck, those are a pain to spot, I'd spend a bunch of time checking everyone over throughly, the diseases that ticks can cary are no joke (then be extra alert for a while to make sure no weird rashes show up, such as the traditional lyme disease bullseye).

A site that provides some useful info: https://www.tickcheck.com/info/tick-identification