I really thought my district was the ONLY one who didn't automatically allow students access to Google Earth. One day we had it, and the next day students could no longer access it. 😭 When I asked our IT Dept. about it, I was told that they aren't able to turn it on for individual teachers and/or students, even with permission from home because it hasn't been approved district-wide (due to an age restriction), I'm basically out of luck. I've spent so much time creating Virtual Field Trips via Google Earth and not being able to use them in class is so disappointing. 😥 (I teach high school.)
I don't really know the process for beginning of the year paperwork and forms, but when I worked at one school, parents filled out everything from personal contact info to field trip permission slips at the beginning of the year (in one big packet) and turned it in. Maybe you could add a Google consent form to each school's enrollment or orientation materials...? That way, when they turn in everything else for the school, that consent form will be there too.