Hello! Sorry to hear that your potential client is going through that, I always feel so terrible when I get these types of requests.
Do you have a day after price? If so, I would treat it like one of those photoshoots...if not...
I definitely would NOT treat this like just any other photoshoot. Remember, these are going to be on display for their lifetime and will most likely be on display for generations to come as well...
Do you have an hourly rate for your weddings? I would charge by the hour based off that price. Think you'll spend 3 hours with them, charge them for 3 hours of your Wedding Hourly Rate.
I do not personally have an hourly fee as I only provide full day coverage at this point but I know what my hourly fee would be. I came up with this number by taking my Full Day Wedding Collection price and dividing by 10 (average number of hours I spend covering a wedding). I would also deliver all the culled photographs to the client, fully retouched and edited, in this situation --- just like my weddings.
There are so many other variables to factor in as well though. Will you be delivering the photographs with a print release? Will you be showing proofs that they will be able to order from (that means hardly any editing other than tweaking some sliders), and most importantly in my opinion, what type of experience are they looking for and can you give that to them?
In the sage words of my hombre Jerry Ghoinis, "What's priceless tomorrow should be expensive today..."