Need advice on Projector/Screen

I have a small uke group performing in nursing homes. I would like to purchase a Projector and Portable Screen so that the group can eliminate sheet music and music stands. Is that advisable and if so what equipment do I need to purchase. Also, what program do you use to put the music on the screens. Does it need to scroll, or is one screen large enough for people to view most songs.

I've seen lots of projectors, but not sure how many lumens is best, or what size screen I will need. Do I need to purchase a Laptop to connect to or is their some other way?

Thank you all for your help............Bruce

Well, they do make projectors that will fit an Iphone or I pad.
http://www.amazon.com/Pocket-Projector-iPhone-4-Devices/dp/B005Y6DROG

When I have seen groups use projectors they simply have a PDF of the songs they are going play and they have a person either the leader or another person scroll down to the right page.

But this has always been in a jam session type setting, I have not seen it used for an audience. Normally when I see people playing a concert they either have music stands or "know" the songs by heart when there is not a conductor.