Hey mamikapapo.

Just keep the jpegs you already rendered.
They will view fine on the screen as long as it is projected and scaled OPTICLY through the normal, or even digital projectors in the theater.

You will notice no pixelization, as optical scaling only makes it APPEAR that the image has been scaled, when in fact, it has not

This is how a celuliod 35-70mm positive print gets scaled up to fit a screen the size of a large passenger buss

Even HD digital streams are projected this way.