I dont think home consoles will ever have a pinball game. The GC is way too powerful, and i dont see anything they could add to make it push the limits of the system. even if the GC gets a pinball game, nintendo isnt that stupid. it would be third party and not carry the mario name. there are much better GC games anyway. pinball is essentially no more a semi-entertaining type of game that works best on handheld (that way they're more likely to be around whenever you get bored, at home, the office, etc.) Buying something for your mom is much diff than for others. i dont know about you, but my mom is a bit more peace-loving than i am, and might not enjoy shooter games like metroid prime (that may be a bad example, as she would love the downloadable chozo lore). I recommend games like animal crossing and perhaps pokemon (it puts a bit of a peaceful, loving competition mood around the fighting, and colloseum especially is about 'purifying' evil 'shadow' pokemon. Zelda would be a good choice, despite the hackin & slashin, it has an awesome, 'mystical' storyline. my aunt wants me to take out the details of windwaker into a short story so that she can read it without playing the game.
also, i would recommend getting her a gameboy rather than GameCube, as it harbors more puzzle/adventure/not-so-detailed-blood&gore-graphics that most grown women i know prefer over the typical GC games.