Sounds like by the end of day Tuesday you will have a lot more snow than the hills. Not a good start for out there as all the storms seem to be hitting the SE part.
As far as your daughter goes, no age limit to ride the trails but when she comes to a road crossing you will need to drive her across. My kids have been riding on their own out there since they were 9-10 years old with no issues. There's been more than a handful of times I've had young Sno-X wannabe's come zipping around a corner on the wrong side, that's probably my biggest fear is those that don't use their heads and think of what's coming around the corner or on the other side of the hill.