No need for two screens. Both 3D and regular 2D will work just fine on a standard screen. With good light control and an ultra high contrast, deep black projector like the Epson 5010, a standard white material is all you need as well. Gone are the days where a grey or "high contrast" screen were necessary. Good mid-level projectors these days don't need any help to produce deep blacks and high contrast.
One thing I will say, if you plan to watch a lot of 3D, the 5010 might not be your best choice. The reason is because the 5010 and 6010 turn off the dynamic iris in 3D mode. Doing so allows them to output more light, but you lose the super deep blacks and the high on/off contrast. You get back the deep blacks to some extent due to the 3D glasses, but the image in 3D just doesn't have quite the same pop and contrast as the regular 2D image without the dynamic iris.
So the best way to think of the 5010 is as a very very good 2D projector that can do 3D in a pinch. The best thing about the 5010 is that it can pump out a lot of light, making it a good choice for larger screen sizes or rooms with a bit of ambient light. If you want to watch a lot of 3D though, the Panasonic PT-AE7000 is the better choice, IMO. It's not quite as bright, but certainly bright enough for 110" in a light controlled room. And its dynamic iris stays active in 3D mode
Also, if you're getting a fixed frame or tensioned electric screen, consider spending a bit extra and getting an acoustically transparent screen. I always prefer to use an acoustically transparent screen whenever possible. For one thing, an AT screen allows you to get the best possible center speaker placement at ear level behind the screen, rather than the typical way down below or way up above the screen center speaker placement. You can also get better room acoustics by placing absorption panels behind the AT screen, rather than having that huge, flat, acoustically reflective surface at the front of the room.
Elite Screens has their AcousticPro1080 material, which is about the least expensive acoustically transparent material in the market. Well worth it, IMO