"Best" is often a matter of personal preference.
D is the newest, very nice tarmac views, large, plenty of computers and seating, same food and beverages on offer as at the others.
A,
C and
D (not B) have children's rooms.
A is the old international lounge, and for those of us returning from a long or redeye flight, it offers the less-used but best "rain" type showers and a workout room. It has a quiet area that has comfortable seating with ottomans, though they removed the Bose music stations with headsets some time ago, and two TV lounges. It may be the least-used club because of its location. (When you enter the AC lobby from the elevators, turn around and to your left is the old Arrivals Lounge, to your right the old Flagship Lounge - the latter is now the AA employee NRTSA lounge, iirc.)
Traveling with a child, some of us would look at our connections first - e.g. arrive at C, depart A, go to A to wait for the departure, rather than looking for a "best" seeking the most convenient, as there are not so many major differences other than what is posted above (if I have missed anything, more knowledgeable members will be along soon enough to fil lin gaps).
Caveat: With a one day pass, unless it is a pass I have not seen that specifically states you have a guest privilege, I do not believe you are allowed any guests (unlike the thirty day or annual membership) other than your young child. You will be able to use other Clubs on your day of travel.
Threads of interest to you (clickable links):
Admirals Club 1 day pass and 30 day membership questions >=2012 (consolidated)
AA's 'better' US lounges / Admirals Club.
DFW / Dallas Fort Worth Admirals Club / Clubs (consolidated)
Originally Posted by
SANbound
I haven't flown a whole lot of AA flights (my flying has mostly been NW/DL to MSP for family reasons and WN around LAS/PHX/SAN for work) in my life. I booked a trip on AA to BOS through DFW for my family in September. We'll be arriving from SAN on AA 1100 and returning from BOS on AA 1365 with 2+ hour layovers in each direction. I have 2 AC passes from a recent Citi AA card signup and was planning on using one in each direction. From searching the FT forums, it seems I should be able to get my wife and daughter (2 1/2 at the time of travel) in on one pass. I realize there are several AC's in DFW... does anyone have a recommendation on the best one for us given the terminals we'll most likely be arriving at and considering that we have a child with us? We're just looking for a place to avoid heavy crowds and hang out for a bit.