I use the free version of iControl DCS on a 1st gen 16gb wifi iPad, you certainly need good and stable wifi connection and even then sometimes a single mfd might freeze (might just be in the free version, fixes itself when changing pages)
Also the MFDs are not really sharp on the iPad (exported at 300x300, rendered at 512), i use it more for the buttons than for the displays.
It is probably better to get the cougar MFDs and, if you really need it, some small screens for them.
PS: there is no way to connect it without Wifi