Like most places in Tokyo,
Roppongi Hills is a bit of a maze, but once you locate a map (thankfully, there are many in English), you will find real treasures in terms of shopping for your baby. In keeping with the Japanese obsession with the French, the mall is filled with quaint french styles for nurseries, and funky toys and wearables!
Harajuku is one of Tokyo's most fun shopping neighborhoods and the best news is that its train station is totally baby-friendly (can't say the same about Shibuya and this note DOES NOT apply to rush hour during which all sane human beings should be safely ensconced in their hotel or nearest karaoke bar!). The pavements on the main street are wide and even the side streets are walkable with prams. As all over Tokyo, however, meals will be a problem so best to pack your own or stock up on
Only Organics jars, as I did!
Other posts in the Tokyo series:
Japan - General Travel Tips
Tokyo, Japan - Karaoke is baby-friendly!
Tokyo, Japan - New York Grill: All High, No Chair
Tokyo, Japan - Cerulean Hotel: Pretty Good!