A.H.
Are there any flowers or anything? You might try some pictures of him handing you a flower he picked. Maybe a shot of you swinging him around, looking at the clouds, skipping rocks in the creek. If the beams are horizontal, you could maybe get a shot of him walking on the beams with you holding his hand. You might get a cute shot of the two of you walking into the creek with your pants legs rolled up, if it's not too cold. Another cute shot may be a shot of your feet with the grass between your toes. Maybe just his, I wouldn't want my feet photographed....haha! As far as clothes, I would wear some nice clothes, maybe khakis and a nice shirt for some of the shots and then some more casual clothes for some of the other shots. I hope those ideas helped, if nothing else maybe it'll spark a better idea! Good luck and have fun with the photo shoot!