Satoshi and Takeshi are a bit more polite when addressing Hikari's mom. In the English dub, they call her by her first name. It's generally considered polite for younger children not to address adults by their given name.
The Japanese original had the insert song Kimi no Soba de (New Arranged Version) as a way to tie Hikari's journey together. The song was originally the first ending theme to the Japanese series. The English dub replace the insert song with a new one called: "The Ultimate Challenge".