If you want to enlarge bitmaps without pixelization then you need to get a package that uses a spline fit algorithm. I use PhotoZoom Pro, there are others. Using this sort of package you can enlarge some pretty nasty images. But what you see is sort of what you get. It won't make anything better, just make what you have larger.and may add a bit of pixel bloom, depending.
In general, when you enlarge a bitmap pixels must be added, there's no way around it. How they are added and what colors they should be depend very much on what algorithm you're using. Some are better than others. A whole lot better.
