If you want to benefit from the rooms the guests will pay for, it's worthwhile doing this whole thing through Marriott Meetings. It's more work for you, but you will reap some points for your efforts.

Basically you need to coordinate all the rooms to one master contract. You can still stipulate individual pay - meaning each person has to present a personal credit card on arrival - but all the spend will count towards your Marriott account. The downside is that you need to coordinate a list of who is staying, when they're checking in, when they're checking out, room preference (one king, two queens ...). The contract will also stipulate minimum room nights subject to a small variance; typically 10%.

So for example, if you have 50 guests checking in and staying 2 nights each, that's 100 room nights. The contract will stipulate that you're on the hook for 100 room nights, subject to a 10% variance = 10 room nights. So this means you could have only 45 guests show up (x2 nights each = 90 room nights) and still be contractually OK. If only 44 guests show up, you are responsible for paying those room nights as per the contract.

Note - the hotel doesn't care who pays for the rooms. They just want to be paid for x room nights total.

If you absolutely want to maximize points from this, then you should master bill everything (all charges go to one account and only one account) then charge back your guests after the fact. (Dear guest - thanks for coming to the wedding. Please pay me $1000.) You decide if this approach is worthwhile ...

Regardless, if you go through Marriott Meetings, you can likely get some sort of room discount depending on the number of room nights you generate, the total amount you spend on catering etc. Basically the more you spend at the hotel, the lower the room rates will go. You'll get a special SET code (or whatever they're called now in Marriott-speak) that guests can use while registering for their rooms to guarantee a lower rate vs whatever is published on the website.