Please check for any errors and correct them for me.

Question

Enclosed is the information you requested concerning our float trips down the Colorado River in the Grand Canyon. All departure dates and prices for the various trips are listed in our booklet. At this time the trips leaving on July 10, July 12, August 2, and August 9 are full.
Minor children below the age of nine may not participate in the float trips. Minor children between the ages of nine and 16 may participate in the float trips, if they are accomplished by a parent.
If you have any other questions after you have read the enclosed booklet, please let me know. We look forward to hosting your voyage through the magnificent Grand Canyon.

Answer 1

Rennell, Angie, Brown --- ??

http://grammar.ccc.commnet.edu/grammar/numbers.htm

http://grammar.ccc.commnet.edu/grammar/commas.htm

Answer 2

do a common go between trip,do
At this time,
Do I suppose to put July 10 th, July 12th, August 2nd, and August 9th.

Answer 3

Numbers:
You have "nine" and "16" -- both need to be spelled out. And no, you should not use ordinal numbers for dates; the dates are fine as you have them.

Comma: <~~note the spelling
"At this time, ... "

Answer 4

between trips, down