You should be, but it all depends on where you play. I don't know much about Northern Michigan fields, but I know several people here that do (SamBam, Kkoerber, djstavich....) PM one of them and/or ask around in the States area under Northern Michigan, theres already a thread there. They may also respond here soon. But I can't answer too well, But some sites require anybody under 18 to have a signed waiver, have their parents accompany them, have gun limits, etc....
It varys on each site.