Your question raises two separate issues, those being the frame itself and, in your case, conversion of the images from traditional photography (prints, slides and/or negatives) to digital images. As an aside, I'd add that it is WAY too late to be doing this as a gift for this Christmas, at least one that will be completed.
Lets discuss the frame first.
First comment, I'd simply rule out, out of hand, any frame that has a "widescreen shape". I can't understand where the manufacturer's heads are at on this issue (well, I kind of do know where ....) but photographs simply are not taken in "widescreen" mode.
Second, I'd go for a fairly large frame, 8" (absolute minimum, and preferably 10" ... as a MINIMUM) to 15". A 15" frame will cost $200 to $250, so size definitely gets pricy.
Not all frames are created equal, by a longshot. Some of them are, well, just plain crappy. Issues include viewing angle (some are TERRIBLE), contrast/brightness/color rendition, how the frame deals with images that don't fit the screen (God help you if it "stretches" ("distorts" would be a better word) images to force a fit), how the frame deals with portrait vs. landscape orientation, etc. Features are big factor ... some frames will play videos with sound, or music to accompany a slide show. Some frames come with a remote control. Some frames have internal memory only, some have no internal memory and use card slots for everything, and some have both internal memory and card slots. Some frames have other functions, like "clock", for example.
I don't want to recommend specific brands or models, but the best way to evaluate a frame is to take your own memory card in and see how your pictures look on the frame. But this isn't always possible or permitted.
Other factors include the type, size and weight of the power supply, the thickness of the frame, it's aesthetics, etc. Again, you have to do some evaluation of frames, because, as I said at the outset, they are NOT all created equal.
Now, as to the photos:
First, If you have the original film (negatives or slides), the conversion should ideally be done from those rather than from prints. There are two options there, doing it yourself or having it done. This subject has been discussed before on this web site, and I would refer you back to finding those. When a large number of photos are involved, there is no way to do this that is cheap, fast and low-risk (the "risk" here is sending your photot to a service that sends them to some 3rd world country for processing and they are never seen or heard from again .... it happens). If you do it yourself, you will spend hundreds to possibly over a thousand dollars on equipment that can do it well, and probably hundreds of hours doing the scans. If you have it done you will spend anywere from 15-cents to $1.49 per image, the media will be out of your posession for weeks (sometimes months), there is risk of loss, and the quality may or may not be good. Just one note, if you are doing it yourself, the only equipment that really does this (scanning film) well are film scanners made by Nikon and also some Epson flatbed scanners. Lots of other scanners (most of them, probably) can, nominally scan film, but none of them do a job comparable to the Nikon and Epson products. But all of these solutions are $300 to over $1,000 for the hardware.
If you are going to work from actual print photographs, most good scanners can do this, the quality varies with the quality of the scanner and, to be honest about it, very few people really know how to use a scanner .... how to use things like histograms to set things like brightness, contrast and gamma to really get the best quality out of an image (this applies to all scanners including film scanners). Also, it's not fast ... if you do this well, it's going to take at least a couple (and probably an average of 5) minutes per image. That doesn't sound like much if you only have a few to do, but if you have thosands of images (and just 50 rolls of film turns into thousands of images), it becomes a big deal.
One point also worth mentioning is that if you are doing this only for the digital photo frame, you really are after, surprisingly, a low-resolution image. Most rectangular frames are 800x600 or 1024x768, and both of those resolutions are well under one megapixel. But if you are doing it as part of a general archiving of your family photos, then you want to create 6 to 10 megapixel images of the entire film image, which will also not be the same shape as the photo frame. What I did in a situation similar to yours was take the archived high resolution images and "resample" an 800x600 "crop" from the 6 to 10 megapixel image. These cropped images "fit" the frame perfectly (e.g. the photo was now exactly the same shape as the digital photo frame), and it also took up relatively little storage (30 of the full size images would have filled the frame's internal memory, but by doing this the frame would hold over 1,000 images in the same memory). But, again, it was a lot of work.
If you are going to use a service for scanning film, the one I would probably recommend is scancafe. I don't have a specific recommendation on print scanning services. Ideally I'd get the image conversions done first so that you can put the digital images on a card that you use to test frames that you are looking at, but at this point that all but rules out having this in time for this Christmas.