Size of the projection is really just about distance. You can get any size you want by putting the projector far enough away, but eventually brightness becomes an issue even in otherwise favorable conditions due to the inverse square law. Short throw projectors are increasingly available if you can't physically get the projector far enough away for your desired size. Projector specs should include recommended throw range and what sizes you can achieve in that range.
The success of the effect will very much depend on how much ambient light there is in the environment, daylight is going to be real hard to compete with, and even moderate lighting may need to be adjusted to avoid hitting the projection surface. This is the biggest disadvantage to projection versus other display technologies: you need a nice reflective surface to project on, but this surface is going to be equally effective at reflecting other sources of visible light, so the only solution is to control the environment around the screen (or rear project, but that tends to be hard to arrange in a home).
Be aware that if you choose a lamp-based projector, these tend to have a live of a few thousand hours before needing the lamp replaced. That's a long time when used for a few hours of presentations a week, but if it's just sitting there on for many hours a day you're going to burn through that a lot more quickly. Cheap office-grade projectors may also have other objections to being on for that long at a stretch. I'm not sure what the current state of consumer LED/laser source projectors is these days, but if you can find one that's bright enough for your purposes that might be a better bet.