Half par 3s and half par 4s. No 5s, beginners can't string together enough decent shots for a hole that long. I agree with Tom about the lack of bunkers, one thing I'd add to what he said is that beginners will probably not be very good about raking them so not only do they have to hit a shot they have no clue how to hit, they'll have to do it out of a footprint half the time!
You want to minimize the amount of time they'll spend looking for balls, so no unmaintained areas, and the only water should be maybe one small pond to carry on one of the par 4s (by "small" I'm talking like a 50 yard carry) and maybe one par 3 with a water carry front and left but which allows a bailout to the right for those who can't make the shot or slice it (sorry lefties!) A little creek meandering through the property can be fun, but hopefully it can be limited to running alongside fairways or crossing in front of a green, rather than crossing in the middle of a fairway. OB is fine - the course has to have edges somewhere - but give it lots of room if there are houses or roads on the OB, and put up fences on all the property lines so people aren't encouraged to go off the reservation to get back their xxx outs
There should be few trees. Single rows of tees to separate fairways (so you know when you're hitting out of another fairway) are fine, but no thick stands. Any doglegs should be gentle, a 90* dogleg won't make sense to them, they'll aim at the green if they can see it or know where it is! The fairway starts right off the teebox, if you top it 10 yards off the tee you shouldn't have to hit out of rough, even nice friendly rough that's kept down to 2" or less.
Mounds would make some good greenside hazards but I'd not go crazy with them and definitely avoid having them in the front 1/4 of the green since beginners will often be approaching from some weird angles and they don't need the added frustration of a mound rejecting their ball trying to roll onto the green. I don't think the greens should be huge, beginners aren't much better at long putts than they are with chips, so you don't really want to give them a lot of 60+ foot putts that they'll probably end up four putting. Plus big greens would require higher greens fees, and the course needs to be inexpensive.
Basically the way I look at it, a beginner course is to get players to the point where they can go round nine holes without any scores in the double digits and maybe make one bogey a round. Once they're at that point they're ready for an easy "real" course and would be able to get their ball around well enough that they wouldn't hold up play.
Maybe I'm dreaming, but having some hours where only walkers are allowed (with free trolley rental) might encourage people to walk. If they are riding from day one of playing, they are probably cartballers forever.