Headroom:
Ad hoc and infrastructure modes are incompatible, meaning you cannot connect a WiFi shield Lin ad hoc mode to an Access Point (infrastructure mode).When you are scanning you are likely scanning for infrastructure mode networks or in other words for APs within range. Most WiFi networks are operated in infrastructure mode.
From your description I am gathering that you want to provide your user with comfort functions similar to connecting your iPhone ( or Android phone) to a given WiFi network. On an iOS device you go into "Settings -> WiFi" and ther are you presented with a list of available WiFi networks that you could connect to. What you are seeing in that in that list are Access points.
Then you want the user to select which network to connect to and depending on that networks settings provide a password.Once you are connected to a network, provided these devices Support Bonjour, you can see what services are offered and other devices can see what services are bing offered by your device.
I am, not sure that can be easily done with any WiFi shield as the Arduino DHCP/Bonjour libraries depend on the Arduino Ethernet library and thus you need an Arduino Ethernet shield. But you can easily connect a little pocket router, e.g. A TP Link TP 702 router?
However I am sure that soon the newly released Arduino WiFi shield will provide a lot of functionality that was previously not available.
Let me see if i can explain my self better..
I want my arduino device to behave like an access point.. So that my user in his computer will see it as a wifi access point for him to connect to.. So that this is easier to configure the device with a web browser...
The problem is that my device will not have a screen or keyboard.. So how can the user configure the device to connect to a wifi network that is protected with password? The only way or easiest way is for my arduino device to behave like an access point "ad-hoc" so that the first time the user configures the password for his home or office access point... Next boot the arduino device will attempt to connect to the configured access point....
Do you know when will the new WIFI shield be released or if theres one coming?