I think all of the more recent Vango drive aways have a similar design such that they free stand well. We always pitch our Kella as you describe but use the Fiamma awning to make attachment easier (roll out a little to attach and then roll back in to tension) but the videos showing attachment to van first do make it look a bit easier so we'll give it a go to compare.I also have the pestering 3 year old! Luckily we can distract her temporarily by giving her a baby to prod.
The Galli feels a lot more like a tent that attaches to the van than our old one, which was very much reliant on the van to stand up. I actually find it easier to put it up without attaching it, and can do this by myself, while it took two of us using the attach first then inflate method. The latter is definitely better in terms of tautness. I did end up moving a few corner pegs etc afterwards, which helped.
When we first put it up we tried to manoeuvre the van into position rather than moving the already pegged out tent, which was a big error, and took ages.
I really like the look of the Galli but, for us, it's far too big - we already only use the Kella if staying somewhere for at least 3 nights. Maybe if we were sleeping out there we might consider it but not lugging 30kg tents around and the faff of pitching/taking down was the main reason we switched from tents to a camper van. Another thing that puts me off is that, at least on the pictures I've seen, there is no door at the back of the tunnel - I use an external gas point on my van situated behind the sliding door and having to walk around the van and/or awning to connect up and when cooking and/or accessing the back would do my head in lol.