I very, very, very strongly advise him to delay entry until AFTER the 9th of August...by a couple days. You do NOT want to go through removal of conditions. He can mention it to the CBP officer, but the officer doesn't make the determination between 2 or 10 year card. If he enters after 2 years of marriage, USCIS will, excluding a mistake, issue a 10 year Green Card regardless of how the CBP officer stamps the passport.