Cum bomb in my stepsister's open fuck mouth

This perverted dirty idea comes from me this time :). Normally my stepsister is known for coming up with the craziest and most perverse fuck ideas. But this time it's my turn. The idea: My stepsister is lying on the floor with her fuck-mouth wide open, waiting with a wet cunt for the cum bomb that's about to squirt down from above. The guy is kneeling above her with a full sack. My job is to empty this sack to the last drop so that my stepsister down on the floor gets a mega cum rain in her mouth. To achieve this, the cock and prostate must be properly penetrated. To do this, I lick his arse, wank his cock nice and hard and shove a thick dildo into his tight arse cunt. Inserting the dildo makes his cock twice as hard and you can feel it immediately. Now I fuck the guy with the dildo and wank his cock at the same time. At the same time, an open fuck mouth is waiting below for the load. My God! What a hot job