Applying H4-COS along with H1b amendment processing. which will be considered first and which will be denied and final status

I am working with employer X from 2014 on h1b with i797 validity till 2017 and he recently filed h1b amendment which is still in process. Now I decided to change my status to H4, So I am asking my husband to file H4-COS, H4-EAD along with his H1b extension in premium process next week from his employer Y. His attorney is saying to him, it is risky to add my H4-COS along with his h1b extension, since my h1b amendment is pending. I am confused whether go a head with H4-COS along with his h1b extension or not.