I think you will be okay.
I think your wife and your kid will be okay since your lawyer said the receipt date on your wife and kid's 485 is August 9, 2004 (before your approval date -- August 12, 2004). For yourself, just go for stamping.
By the way, yes your wife's H4 and your kid's H4 status are gone automatically because of your I-485 approval, but if your wife and your kids are still in U.S., their status is still legal (not out of status) because of their AOS status. If they are outside U.S., they will need their valid Advanced Parole (I hope your wife and your kid have valid AP travel document). (Suggestion: if they are in U.S. with you, don't let them leave U.S. until their 485 is approved because we are not sure about receipt date vs approval date. Just clarify with people of this forum or lawyers or Rajiv Khanna of immigration.com).
I am curious. When did you file your own I-485? Why didn't you file for your wife and your kid earlier? One day after my spouse and I got married, I filed immediately for my spouse (just 3 months before my 485 was approved.) My spouse got my spouse's 485 approval in 1 year and 7 months. But if you are lucky, it can be faster (Immigration service are working on reducing backlogs as a part of their goal.)
But don't worry. Everything will be fine. There is a bill (called "Solve Act of 2004"), that is introduced by the House of Representative and Senate, to bring permanent resident's spouse and kid(S) to "no waiting list" like US citizen's spouse and kid(s). Immediate relatives will be exempted from counting towards the 480,000 ceiling on family-based immigrant visas and include immediate relatives of permanent residents. House of Representatives and Senators are still reviewing and debating. I don't know how long it will take to pass the bill. Just stay tuned.
Good luck.
USGC485