Entering with H-4 would not affect his I-485 case.

Since H visa holder can have dual-intent.
It is strongly recommended that he get I-485 receipt before leaving US. Being physically out of US without I-485 receipt constitutes ground for denial.
Since he is just a dependent, usually he is free to come and go with either H-4 visa or AP. In either case, it itself wouldn't affect his I-485 case.
Because he comes over for only a couple of weeks, it is up to you two to decide whether to apply AP. Because USCIS might deny AP application if they find out he is out of US while AP is being processed. But again, denial of AP itself wouldn't affect his I-485 case. It only means he must get H-4 visa first before entering again. In this case, if he fails to get H-4 visa, his I-485 case may be denied because he is not physically in US while the I-485 case is being adjudicated.
Do remember, even after he gets his green card, he has to meet resident requirement to keep the green card.

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• 回复：Entering with H-4 would not affect his I-485 case. -IamH-1b,filed485- ♀ (20 bytes) () 10/26/2007 postreply 06:54:23