The difficulty you'll have is primarily tides and lack of equipment. The reason I say this is because most of the flatwater is quite far up north before the river mouth. I wouldn't go anywhere near that river mouth. From what I hear its crocs galore. The first issue is the tides. If you look at the arrow furthest south on my diagram, that is where the kitesurfari guys camp and when they drive in, they have to drive in at low tide and they're locked in when the tide is high. That will make it tough for you because you're going to have to drive (or have a really long walk) in and out and I wouldn't want to be walking in a croc area at night. I don't think you can camp in other locations so I don't think you'll have the ability to just set up camp in a random spot along that coastline. The second issue is most of the really good flatwater spots are accessed by the kitesurfari guys using unimog's and boats so if you don't have access to either of these, its going to limit your access to these spots and the amount of time you have at these. We used to kite downwind to these locations and then go back on the unimog.

As Saffer said Drive in at low tide. Kite while mid to high. Drive out as it gets low again. Check tide times for your visit dates. If that timing doesn't suit then don't go.

I went on the kitesurfari but my experience was different. Good wind and food and a decent place to sleep but limited locations to kite. They never fired up the argo or boat, offered to organise any downinders or take us to the wave spot. We kited the whole trip out front of camp which after a few days leaves you wanting. We paid $1350 plus flights so almost $1850 and will be looking at Aitutaki or Sri Lanka next time for little more but will probably going for 10-14days instead of 4. It was fun but won't be doing it again.