Why do we avoid making the Bracha of Kiddush Levanah on Friday night and the nights of Yomim Tovim?
1 - Although L'Chatchila we do not make Kiddush Levana Friday night and on nights of Yom Tov, if the forecast for after this night is cloudy, or if it is the last night you may do it on those nights.
2 - The reasons given not to make Kiddush Levana on Friday night are as follows.
A: Maharil, MaHara M'Pano, Sefer Agada - Just like there are Techum issues in this world, there are also Techum issues above, and it is inappropiate to greet the Shechina out of the Techum. The Radbaz says that this is a weak reason not to do Kiddush Levana on these nights.
B: MaHara M'Pano - Since Kovod Shabbos and Kedushas Yom Tov are more than greeting the Levana, we do not mix two Simchos.
C: Minhagei Maharil - Birchas HaLevana is like a Techina, which we do not say on Yom Tov.
D: Sdei Chemed - You may come to carry the Siddur into Reshus HaRabim on Shabbos.
E: Rashba - It is a Taam Sod.