Let me make sure I've got this right. Your scenario is:
- A new 29g with 3ppm ammonia in the water for a fishless cycle
- A Whisper filter you've seeded for a week on an established tank
- A new AC50
If that's the case, you're off to a good start. You don't need to do anything but keep an eye on your ammonia levels. I'm not sure seeding a filter for a week will do much, but it can only help. Gravel from the cycled tank will help, filter media from the cycled tank would help more. I keep extra bags of biomedia in my filters to help seed new tanks. I've cycled a 40B in a week when seeding with the biomedia.
Water from a cycled tank won't do much. The beneficial bacteria live on surfaces in the tank. There are few if any in the water column.