wow your house is big to be able to accommodate that many people! anyway tama ka sis, a mom would make everything special for her child talaga.
i think you should set a budget first. mga GT sisses natin iba iba ang range ng budget but almost every party is a success naman. if you're creative, malaki masa-save mo if you do stuff by yourself (and your relatives, friends, and yayas) stuff like invitations, name tags, thank you tags, candy corner, balloons, kid's menu, etc. if you dont have time to diy...
i suggest you choose a theme that's popular. that's what i realized now that i'm almost done with my party preps. my theme is chocolate factory so walang m&m's or kitkat ka makikita sa divi halos. nagpagawa pa tuloy ako ng sling bag coz i don't want naman theme ko chocolate tapos lootbag ko minnie mouse.

tapos invitation ko may extra fee pa for layout coz special request. wala sa pool of ready layouts ang theme ko.
if disney princess, tinkerbell, hello kitty, mickey mouse, sponge bob, pooh, etc ang theme mo, ang bilis makakita ng lootbags and toys and stickers sa divisoria. all in theme kaya fun! the invitation din mabilis and mas tipid. the plastic bag (paper bag style) na may character nasa 12-18 pesos each. ganun din yung small backpack. then mga statio, stickers, coloring book, small toys madami din. 5-15pesos yata. sa 2nd floor i saw small toys for 7.50 each. ang prizes ko sa ground floor ranging from 15-35 each per toy. sa
divi mall ka pumunta sis. you can park your car at 168 (para safe) then tricycle to divi mall nalang.
personally, ang budget namin ni hubby for our party is 300k (sana hindi umabot dun

) pero may venue rental kami (maliit lang kasi place ko hehe) and 400/head napili ni hubby na food for adults. more or less 150 adults din kami excluding kids. tapos gusto ko medyo bongga ang balloon and venue decors so dun din napunta bulk of the budget. plus it's also her baptism. if you decide on this budget, i can pm you how much i spent per category to give you an idea. hope this helps!