Thanks for the reply. I haven't decided which sound recording program I'll use long run, but I did download an app called Awesome Voice Recorder, and have tried it with the internal mics:
https://itunes.apple.com/ca/app/awesome-voice-recorder/id892208399?mt=8 It seems to do a good job and is simple to operate, and for some strange reason sounded better than the stock voice recorder found on the phone.
For more sophisticated recording (multitrack, editing, etc.) I would imagine there are enough choices of recording apps to boggle anyone. I am not very tech savvy, so I'll be siding with a recording app that is simple to use. As coincidence would have it, I have a Focusrite Saffire 6 USB audio interface I used with my Lenovo notebook (similar to the one you linked) which is a bit older now, but always served me well for my very modest requirements. I was hoping that there would be a way to connect two mics to the phone without using an interface, just to stay minimalist, but I'm not sure if this possible or what I'd be losing if I did so. The only thing that jumps out as necessitating an interface would be the need for phantom power, but I'm going to stick with passive mics.