There are no limits on the tangible assets when you entering to or exiting from USA. Although, the assets that you carry with you exceeds in equivalent cash amount of $10,000, you have the obligation to declare that amount. In case of carrying over than $10,000 FinCEN 105 Form should be filled in “ Report of International Transportation of Currency and Monetary Instruments".
Even though family members carry separately and different amount less than 10,000 dollars, in case of total amount exceeds $10,000, obligation of declaration continues. For example, one of the family member carries $5,000 and the other carries $6,000, this amounts considered as $11,000 total and it is an obligated to fill FinCEN form. The amount you carry and not declare with FinCEN form, could be seized by the officer and the person can be sentenced by law as criminal.
IMPORTANT NOTICE: The CBP Form 6059-B that is given to those who arrives to USA, won't be given to those who left USA. Although you have the same obligation to declare the value of the amount that they carry if the amount exceeds $10,000.