My son had to amend his taxes to change the option that someone can claim him today. when can I complete my taxes to claim him as a dependent?

You will have to print your return out on paper and file it by mail. It takes the IRS 4 months or more to process an amended return, so their records will not be updated in time for you to e-file before the April deadline. Print your return and file it by mail on or before April 18, 2017.

You can't e-File in any case because your son's  incorrect return will prevent that. Both returns will have to go by US Mail.