Perhaps you could have an assistant run a slideshow on your laptop at the event.
You could possibly do this during dinner when really nothing much is going on, &you could have a captive audience.
As you take your table shots, hand everyone a pre-printed card with information on the fact that they can place an order today by stopping by to see you wherever you set up! I also have a dye sub printer that I can print right there up to an 8X10.
You will need to run this by the bride & groom As A Thank You I also make a small wallet album for the bride & groom to take with them after the reception. You can do well if you have the assistant and are not obtrusive to the goings on of the wedding.....
Just a different solution to showing proofs and going on-line.....

If you do provide proofs, I would put a water mark across them so they couldn't scan them. I haven't gotten into post production yet, so don't know what tools are out there that would enable them to remove the watermarks. Maybe some of the Photoshop or other software wizards out there could educate me/us on that. Cheers.

I believe they asked for a proof book so that they could take the images away with them, copy what they wanted and return it to you with little to no orders coming your way, from them.

How long have you been in business/doing weddings? If these people can get a proof book to these so-called non computer savvy relatives/friends, then they can get a laptop over to them and show them the images. Just take them out to a local McDs or coffee shop that has WiFi.

Something sounds fishy to me and I'm surprised you may not be noticing this. How many weddings have you done and hwat have you done in the past with these wedding customers regarding the wedding images?

Charge for the proof book (or a deposit if you want it back) can you add a tear out order form to the proof book? Sorry I haven't shot a wedding (non-pro here).