No, you are not required to use the loopback provision.  It is basically a provision that allows those affected by the Hurricane disasters to see a measure of relief on their tax returns.  If you made more money in 2016 than 2017, live in an area declared by law and recognized by the IRS to qualify for the provision, you may utilize the loopback provision if you will see a larger refund that way.  Otherwise, you may choose the standard calculation for EITC and the Child Tax credit if that calculation results in a greater tax savings (or greater refund). 

Click on this link for more information from the IRS on Hurricane Relief Provisions.