How big of a tent do I need?

I would definitely call a text company to ask for sure instead of just asking here.....but I don't think that tent is big enough for what you need.

Almost. Each 10 top with chairs needs 100 sq. feet, as does each buffet table and each bar. That is assuming you seat everyone at tables for 10. it might? but if there is any lost space under that tent, you might not make it.

Your best bet is to call the manor house, find out who works there for tents, and call them.

My venue is actually in a state park so everything like tent, tables, and chairs is up to me. My venue may be able to recommend some vendors in the area. The main vendor I have searched has a 20 x 40 tent as being enough room for 80-90 guests.

10 tables of 8, a sweetheart table, and 3 additional buffet/beverage tables should fit in a 40 x 40 or 30 x 50 tent. Each table we'll count as 100 square feet (sweetheart table won't need that much) so let's say I need 1400 square feet. 40 x 40 tent is 1600 square feet so it should be plenty. I have asked a potential vendor for an example floor plan. The cake table, gift table, and dance floor are inside the house and therefore not under the tent. The tent is in case of rain.