hi priscilla,
suggest ur better do it before 25-jul cos it's the start of the 7th lunar month. esp ur will only break the news to both parents on ur marriage plan to avoid shock, they may penalise ur for not telling them first n also never avoid such inauspicious month(s) for such important thing (dates-selection).. u never know how they will react since ur dated only for 6 months..
for banquet, u should start sourcing other venues beside HIPV & Pines as back-ups.. i know Pines can hold up to 42 tables.. it depends on how many tables ur want.. if u hv the max confirmed table nos needed, u can base on this number to book venue... to gauge the no, u can first do up a tentertive invitation list for urself, ur FH, ur parents & ur F-PIL..
for date-selections, we took around 2 hrs to calculate. basically, the master will need both ur birthdates (lunar & calendar), birth-time n both parents' birthdates (lunar & calendar).. it's best both u & ur FH can go together to voice up ur preference, eg. weekday or weekends, all-in-one day wedding or split into 2 days, etc... hope this helps.. enjoy ur wedding preps! ^_^