Time Capsule finally installed, not working properly

Finally I managed to set up my Time Capsule (original I had an Airport extreme and a LaCie BackUp), I was able to set up my Fam Tschopp Network and a guest network, I did also run a back up of my laptop data (still oustanding the back up of my husbands Mac).

But since I am on the new WiFI connection with my AirportExtreme/Time Capsule I loose connections as soon as my aupair wants to join the network as well - regardless if she chooses Fam Tschopp WLAN Network or the Guest Network.

a) what is wrong? how can I add my aupairs Window laptop to the WLAN in the house?

b) how can I change the password on Fam Tschopp Wlan (as I gave it to too many people in my old set up) to ensure all besides family members log into the Guest Network

c) I need to amplify the WLAN signals, how to I get my other Airport Extreme devices to be seen in the new setup and work?

d) how to I manage the backup set up on the Time Capsule so it saves my apple laptop data and the Mac of my husband as 2 different things...

Ponidini - if you read did - Switzerland did not die, I was just busy managing my company and my 4 kids, so I postponned my IT issues rather extremely long....