I know that won't take your bid away. My school does bids on Saturday, and last year when I pledged I had to be home on bids day to be at my Grandma's birthday party. I'm not sure how the Greek system is at your school (at mine it's not a super big deal) but I was able to hint that I was going to be home for a majority of the day.
It sounds like because it's a Monday sororities are used to new members not being available for their entire bids day. Have fun and don't stress about it!
