We have an electronic keypad lock on the front door - works fantastic, I wouldn't want to go with keys. It's a different model than Morticia's - I believe we have that model on a door to our private space. It's REALLY loud (not the beeping, but the grinding/motion of the bolt movement). We actually rarely use it, but it's nice that it's there.
We haven't had an issue with guests forgetting, I suppose because we use a number they'd easily remember and we run it for them in person. I can see it would be a challenge for someone unfamiliar who was doing a self-check in.
DH tells me he's found mechanical (no batteries), programmable keypad locks for the guest rooms (we're also planning to put them on the hall baths, to avoid opportunism). Because our codes are guest specific, the code will be the same for front door, guest room door, and bath door (if not en suite). I haven't seen these locks yet (DH hasn't gotten the info to me yet), so I can't tell you if/how they work or even where to order them. Jsut sharing that the option is out there.
I figure that avoiding keys for guests (although WE have physical keys as well as master codes) is one less thing for me to have to keep track of (lost keys, replacement keys, changing locks, lost key charges). I wait until the guests are out the door, scan the room/s for forgotten items, and then I change the code on the front door. Done..