Rogo, no experience with kids on this trail, but I think it would be a good one for kids. Take 5 or 6 days, easy to plan short distance days. Walk early in the morning, swim in the afternoons. It is hot in the arvos for hiking, but cool by the water. All the campsites are beside water - falls, river, waterholes. If crocs were a problem they would not be beside the water (if it were croc territory all but a couple of these campsites would be dangerous as they are too close to the water). Most are shady. Most but not all have toilets. There are Emergency Call Devices (ECDs) at most campsites (refer to maps) - radios to the national park ranger.
The Katherine River was closed whilst I was there, due to a saltie sighting. However the Jatbula only starts at the Katherine River, it does not follow the river at all.
The first day is a climb up the escarpment edge to the plateau above. The rest of the trail is along the plateau until it climbs down again near the end. The climbs are not difficult.
A taxi from Edith Falls to Katherine cost $150 in July this year.
Although I have read only 10 hikers are permitted per day, this was not my experience. I had trouble booking a date, and the only other two people I met on the trail had trouble moving their booking, so we both had the impression it was booked out when we were there. Yes that right, the whole time, there was just 3 of us, and no-one was ahead of us in the previous 2 days.
http://jez-magneticnorth.blogspot.com/2010/08/jatbula-trail.html