As i said before, i was thinking of using an iPad with OTG cable but realise that Wifi is more convenient.
It won’t work you need to have the Apple iAP decryption chip for that to work which requires going through Apples ‘Made for iDevice’ (MFI) program. The WiFI Bridge as documented on this site is the easiest solution to connect to a long range radio. (though using an ESP8266 instead of the XBee Module)
The ESP8266 modules are better. the one you linked was a ESP8266-01 which requires a regulator to power it as its 3.3V. The deal extreme board I linked to has a regulator onboard and a switch to allow easy programming of new firmware. There is developments for better firmware here https://github.com/dogmaphobic/mavesp8266
As for interference from 2.4GHz WiFi and 2.4GHz RC Spread Spectrum radios. You are correct that they can interfere with each other and reduce range. The point is this only really happens when the antennas are close together. I have had no noticeable issues myself using MAVPilot and WiFi/Bridge and RC Control
Most interference issue with range and drones is caused onboard the drone, when you have 2 or more transmitting antennas in very close proximity. This causes the receiving stage of the radios to de-sensitize reducing range. By maximizing the distance between the antennas greatly improves the situation. If you are only using the WiFi to 915MHz bridge you also improve this as then you have only one 2.4GHz radio on the drone (RC Control)
That said people are working on WiFi control from the RC Transmitter. Which will be cool and solve the telemetry and control being then on the same frequency and technology. Then range can be extended with just better and directional antennas. https://www.youtube.com/watch?v=6-0GJ21oUO4
Hope that helps. 🙂