So sorry for you - it's a tough thing to go through but it sounds as though you have a loving supportive family there (although dp may not understand).
The decision on whether to see him afterwards is yours and yours alone - go with your gut instinct and don't let anyone talk you out of what you want to do.
I personally didn't want to see my Mum or Grandparents as I feel that you are just looking at a shell and they've gone anyway but if your last memories are of him being ravaged by cancer then a peaceful face may be good.
Massive hug for you and sending strength for today.