Can I submit the paper to arxiv and the conference at the same time?
Worrying about other people publishing your paper isn't something you should do. One, it's not in your control, that'll happen if it has to happen. Two, even if it does, there are always other parameters which can differentiate the paper.
This conference says you can post it to Arxiv, so go ahead! But I don't really think it'll stop someone else from publishing their material else where. Especially when the pre-print upload date is so close to the conference many might not even realize that their is a paper with the same domain!