Can you give us more than a week to enter? Cheaters are going to figure out ways to cheat (eg. having various materials prepared beforehand) regardless, so you might as well get more people involved by having less of a strict time frame to participate.
I don’t think it’s necessarily a bad thing that some people will spend longer on the hack than others. I personally hosted as a 1 hour / 2 hour blitz and really didn’t care if people spent longer, but a 2 days or 1 week thing sounds fun, too.
I worry that if you limit the participation timeframe so strictly and if users feel like there are high expectations for the hours put in / requirements to meet, that not as many people will be inclined to participate. I want your jam to be successful, so I would recommend you rethink some of these things. You might find something useful from looking at the community events I’ve hosted - I think the most important aspect is inclusion if you want a good turnout.
Best of luck! I’m rooting for you.