If I am ready to start a credential program now, should I pursue the PE credential (for dance) or English (for theatre)?

These are still the designated programs for dance and theatre, so they will allow you to teach in dance or theatre.  Some people recommend that your job prospects are improved if you hold two credentials because a school district can hire you to teach PE and dance or English and theatre while you build your arts program.  This likely to be true in smaller or rural districts.  In order to add a second credential, you will need to take the CSET in the other content area.