You'd also have to ask Spring Valley if they have budgeted for the cost of a third referee times 51 matches. My guess is that would be around $2,000.
There are also 11 club matches at Ballentine that Saturday. Since 3 of those matches are at 10:30 and another 3 at 3:00 PM, at least 9 referees will be needed there. I guess high school age referees could be used for some of these games if they are not all playing in one of the tournaments or watching one of their siblings.
Another issue with referees on the list is that quite a few are parents. I know several referees that will be sitting in the stands watching their daughters play for at least 2 of the matches at Spring Valley on Saturday. I know several others that will be doing the same thing for their sons' matches in the Lake Murray Challenge.