A big birthday bash is in the works for Montgomeryville.   Township officials are planning a full slate of activities to celebrate the tricentennial of their community in 2014.   The actual anniversary at the end of May will be marked with lots of family friendly fun.   An even bigger celebration in September will combine the annual township Autumn Festival with the tricentennial.   The township will fund part of the celebration but the hope is that the business community will step up to the plate in a big way.   A Montgomery 300 web site is in the works and it will offer paying sponsors an opportunity to advertise their goods and services.