Read in
Munich Found that the butterflies inhabit the aquatic plant house until March 16th. Tram 17 takes you there directly. Also, the zoo has an egg hunt on Saturday and Sunday of Easter weekend - 23rd, 24th. 80k eggs are hidden and activities include face painting, puppet theater, and bouncing castle. On Easter Sunday
Olympiapark has an Easter Festival with performances and competitions. Also, March 17th there will be a St Patrick's parade from Leopold and Ludwigstrasse to
Odeonsplatz. Parade leaves at noon from "muchner Freiheit". Ends at 6PM. Also read in Munich Found and read in some past forums that Easter Markets exist.
If the weather is good, I may take my little ones to Lego Land. Never been to the one in Germany but back in Southern California the one is San Diego County is really popular with 2 to 9 year olds.