I know this isn't the answer you are looking for but just a suggestion for measuring the holes: Don't use a wheel. I work in road construction and have assited many surveyors in their construction staking. I can say that without a doubt, unless you are using a wheel on a very smooth surface like a roadway it is very inaccurate. For about $30 or so I bought a 300' Stanley Power winder tape and I got mine from Lowes. Which is probably about the same amount of money or a little less than what most wheels cost.
Get a buddy to come with you and hold the one end of the tape. When the holes are over 300' just pull the tape all the way out and mark on the grass with a dot of marking paint or one of those little orange pylons kids use for soccer or something like that.
If you want to get crazy accurate get yourself a GPS robotic total station with a prism and rod...That'll only set you back $10,000...or more...

You'll be the envy of all the surveyors in the neighborhood.
-DAllen
“This is the captain. We have a little problem with our entry sequence, so we may experience some slight... turbulence and then explode. ”
-Malcolm Reynolds, Serenity