It would help to know more - are you singing? are you playing un-aided acoustic, amplified acoustic, electric? What is your goal for the video?
A personal nitpick:
The DAW term is sort of a catch-all acronym I see in the community. DAW - digital audio workstation - suggests a way to digitize your audio, run it through a piece of software to manipulate it, and create a final music file. This may also merge it with video. It sounds like you just want to record audio with video and not do anything to it other than create the file.
I think I would probably avoid using the iPad mic. it will pick up all kinds of surrounding sounds and will not likely be in an optimal position to get the best sound.
I would also probably avoid recording separate audio and video unless I wanted to manipulate the audio before combining. Combining the two would be a step I’d avoid because it would mean additional process and software I’d need.
When I have recorded myself, I have done it with my 2013 MacBook. It sits on a table in front of me and uses the USB port on my modeler for input. I do not sing. I manipulate the camera to view what I want it to record and use QuickTime for the recording. I think on one recording, I needed to save the file in a specific way for it to play on YouTube.
As for your portable question, see my post here, item #3: Really need amp for beginner - #9 by sequences
Personally, I find tablet apps restrictive. Partially due to the input options, and partially due to the human interface limitations. There are folks here that do use iPads for recording, so hopefully they will add their experiences.