The bringing of the Korbon Pesach Sheni is on the 14th of Iyar (this year, this Wednesday), and it was eaten on the night of the fifteenth (this year, Wednesday night). Tachanun is not said on the fourteenth of Iyar, neither by Shacharis nor by Minchah. It IS said by the Minchah of the 13th. It is also said on the 15th.
Kedushah requires preparation. In fact, the degree of kedusha usually depends on the degree of preparation.By that criterion, we will iyh be davening this Shabbos in an even MORE kadosh Beis Kenesses. May our actions ther, our deportment there, reflect that!