Changing the PPI won't increase the resolution. PPI is not a measure of the actual resolution of an image. PPI is an output resolution (for computer screens). The true resolution of an image is measured in megapixels, your image 1441 x 907 is only 1.3 megapixels.
What you need to do is give them an image at the maximum size it came out of your camera. If you use a point and shoot, make sure the settings are so that the maximum file size and quality is chosen. If it's from a phone camera, then 1.3 megapixels probably the biggest size available.
An image 1441 pixels by 907 is not big enough for anything more than a small print. If you are enlarging it, it will look blurred. If you increase the PPI, it will still be the same size image, and still blurred when you print an enlargement. If you rescale the image by resampling it (to make more pixels) the image will still be blurred. You see where this is going - right?
