Removing background wrinkles

[Katie B]

Hi Damien... I need assistance on the best way to edit the background so you don't see the seamless paper is warped.  My first thought was to convert to a smart layer, add a Gaussian blur and mask off the dad and baby... but I think it's adding banding.   I'll attach both the original and the background edited.  Would love your thoughts on this. Thanks!

[Damien Symonds]

Never try to fix a background like this.  Only replace it.