I won't blame you for extending the trip.

Literal

Trip [object-を] extended [nominalizer-こと] [with-で] you [object-を] won't-blame.

~ことで (because of / for doing X) marks the reason someone might be blamed. 非難する (to blame/criticize) is a formal verb. 延ばす (to extend/postpone) in past こと form describes the completed action.