COB events - what do i wear?

I went through formal recruitment and didn't pledge because the houses i really liked didn't offer me a bid.

about 4 weeks later, today, i got a letter from a house i really liked concerning COB. they've scheduled events for a few nights next week and i definitely want to go!

the events are a barbeque one night, a movie night the next night, and a mini-party at the house with food and music the last night.

i really liked this sorority and getting this letter seriously brightened my day 100% thinking i might have a chance. my only question is, what do i wear? i'm clueless about COB and i know its not AS formal but i dont know if that means you can wear your every day clothes or if you should still dress to impress?

any help greatly appreciated. thanks.