But at that time of the morning, Uber is probably cheaper to the airport (I live in the same arrondissement, and that's been my experience with very early morning Transfers to the airport).
(I am not trying to convince you to take Uber, merely stating my experience going to CDG from the same arrondissement at that time of the morning. My guess is that surge pricing would come into play later in the morning, and in the afternoons, and anytime there's some taxi trouble of traffic problems.). Indeed, in your case it's probably best/easiest to reserve ahead of time on the G7 app for your peace of mind and to have it set and not have to think about it again.