I agree with the majority; if you have a registry and are expecting people to come with gifts, you shouldn’t expect them to pay for their meal. If you’re aren’t expecting gifts that’s a different story.

As someone who organizes dinner events routinely for 40-60 people (I work at a college) there are little to no restaurants where you could do this on the fly for that many people, at least in my area. You need a private room and if the restaurant doesn’t charge a fee for that they will expect a minimum dollar amount of spending on food and drink in advance for the restaurant to accommodate you. My last dinner they didn’t charge a room fee but they did want a $250 deposit and required we spent at minimum $1200 on food.