I've got very pale yellow carpet in my sitting room and a 17 month old... and yet it is still pristeen. Basically shoes aren't permitted, and if tea or coffee is drunk then a cup and saucer is used (not a mug) - because the saucer catches any drips of tea.....
We also don't do 'tv dinners' in there but either eat in the kitchen or dining room. That's all it takes.
If you do get a mark on your carpet use 1001 carpet cleaner.