Implant supported dentures are your best bet for comfort, because lower dentures SUCK in terms of the fit. Upper dentures usually fit pretty well, but lower dentures are always being knocked loose, popping up, rocking, or sliding around.
I would see if you can try doing implants only on the bottom (mandibular) denture, and just leaving the top one as a regular complete denture. Granted, I don't know how much bone your wife has left on her alveolar ridges, but most of the time the issues of fit are with the bottom denture.
The implants are also not going to be the conventional implants for replacing teeth. I am guessing the implants they will be using are what are known as "mini-implants" for the denture abutment attachments, which bear less risk of placement during the surgery.
My best recommendation in terms of saving money would be that dental schools will be your best friend here. I know that my dental school did plenty of implants for super cheap.
If I can remember the prices correctly...
$70 extraction for each tooth (not including nitrous or sedation)
$2000 per implant
$1000 for the two dentures
This is compared to private practice prices
$143-230 extraction per tooth (depending on whether it is simple or surgical)
$5000 per implant
$3600 for the two dentures
Now, know that the investment trade-off is time. Dental students have to get things triple checked by professors, and most of the time have to do their own labwork, writeups, consultations etc. so the process may go kind of slowly. For example, the new patient exam always took two 4 hour sessions for us just due to the amount of waiting in line for professors to check your work. If you are willing to put in the time however, the reduction in price for the treatment is pretty evident. The other advantage is that if the program has professors who are denture specialists (removable prosthodontists) then your case will be under their guidance, and they have a lot more training and education regarding dentures than the general dentist.