You are arranging dinner for six people, including someone who avoids certain ingredients. Call a restaurant and ask three or four questions before booking.
Hello, I'd like to arrange dinner for a group of six next Friday, ideally at around seven in the evening. Do you have a table for six available at that time? One person needs to avoid some ingredients. Who should we speak to about whether suitable dishes are available? Is there a quieter seating area where we can talk comfortably? Do you require a deposit for a group of our size? I haven't confirmed the booking yet because I want to check these details with everyone first. We are happy to arrive a little earlier if that makes the table arrangement easier. I can send the ingredient details in advance rather than trying to explain them while the kitchen is busy on the night. I don't want to assume that removing one visible ingredient makes a dish suitable, so clear information from your team would help.