I'd find as much downed branches as you can and brush it in with that. You probably can't cut and green limbs but if you can break up the pattern with wind blown limbs the deer will grow accustomed to it a lot quicker. People say when you put up a ground blind your changing around a deers living room so they can tell pretty quick. The more you "Brush it in" the better.
Also, I don't know what chairs you are using but Id try to get them as scent free as possible. I use those collapsing camping chairs (the ones that fit in a bag) and try to leave them outdoors for a few weeks as well as spray them down with scent free spray. People take so much time making there clothes scent free then forget to make everything else scent free they bring in the woods!
You did the right thing by asking the park ranger. They're out there all the time and know where the deer are. I talked to one guy one time that worked the front gate of a state park. He said all these hunters would come in and find the farthest place in the woods. One guy finally asked him at the front gate if he's seen any big deer in the last few months. The guy said, "youre the only one that has asked me that, I was waiting for someone." He told the guy that a giant 12 has been walking 40 yards from the front gate everyday or so. Everyone thought the big bucks were hidden in the farthest areas. I guess the guy set up 60 yards from the shack at the front gate a week later and killed that buck. Sometimes you just got to ask!
Hope this helps some. Good luck to you and your son, let us know how he does!