Vans come in different sizes but with only 2 adults and a child, you and the luggage should fit in a normal size--and with your wife minding the child and you minding everything else, for peace of mind, you need to corral all people and stuff into one vehicle. If your six suitcases are pretty full size, then two taxis aren't going to work--you'd need three. Try this service which has been used by other FT'ers (for van) with success:
www.tour-beijing.com
Their cost for one-way transfer is USD 65 and in your situation, absolutely worth it. With proper instructions and taking the address of hotel in Chinese with you, only a driver (non-English speaking) is needed. The driver will meet you outside Customs with a sign with your name on, and help with the luggage carts.

I also second the notion to go directly from airport to apartment if it will be ready (such as a serviced apartment). If your reservation is already set up to begin the next night, or you will be going to a non-serviced apartment that may need supplies in order to be liveable, and you must stay at a hotel for one night, then choose a hotel in town that is relatively close to your temporary apartment. Tell us where this apartment is and we can advise on a suitable hotel. Doing it this way rather than staying at the airport will give you two benefits:
1) Traffic into town and in town will be light late at night, hell the next day. Take advantage of the late hour.
2) Once you are ensconced in a hotel, you can then use much cheaper taxis to ferry your 6 suitcases, stroller, etc. from hotel to temporary apartment. Even if it takes 3 ferry trips, it will be a lot cheaper and less headache than having to hire a van for a second day. Or if you are getting reimbursement or don't mind spending the cash, just hire a van for a half-day the next day to ferry luggage and do errands/pick up household stuff you might need to get set up.

ETA: I've requested that a moderator create a new thread for this topic and move posts 92-96 to it. There have been enough previous posts in a similar vein that it would be useful for the topic to stand alone for current and future discussion and information adds. Thanks.