If you want to put the goldfish in the tank then buy a test kit so you can test the water.
API Master test kit is the best. It will test ammonia/nitrites/nitogen and ph. That way by having the test kit you will be able to see ammonia levels when they rise and be able to perform water changes accordingly.
The only other think I would recommend is bacteria booster such as API's stresszyme. ADD IT RIGHT TO YOUR FILTER! This will jump start the cycling process and will help your tank to cycle faster. Add more once a week.
Also, no matter how cute they are and how much your daughter begs PLEASE do not buy any more goldfish for about a month or so until this tank is cycled. Ammonia and nitrites should read zero and Ph you want around 7.2-8.0 (alkaline) nitrates no higher than 40 mg/l. Then it is safe to add another fish!
Also, I use a water condtioner by aqueon and it keeps ammonia and nitrites at a minimum. I love it! And you can use it with the API stresszyme! I've never had tanks cycle so quickly before! Good Luck and keep us posted and ask any questions if you think of any. Someone will answer and try to help!
POST PIX! WE love PIX!!