My understanding is that the ability to switch off the airbag is only important when using a rear-facing child seat. You’ll have to check the local legislation, but usually a child has to be rear-facing for a minimum of the first six months.
We planned to keep our kids rear-facing for the first year, but they were both too big to sit comfortably in a rear-facing capsule by about nine months. The limitation wasn’t the size of the car (Jaguar F Pace), rather their leg lengths.
I don't have the switch to disengage the airbag in my Zed nor isofix, but I’m happy to put my daughter in the car on a booster seat.
The booster seat uses only a conventional lap and sash belt to secure both the child and the seat, but I have a device called a CG Lock (now discontinued) that statically locks the lap belt. I have them in all our (fun) cars because they anchor the driver’s bum into the seat as well as a harness does, whilst allowing upper body movement to lean forward and see out of junctions, adjust the heater etc. By statically locking the lap belt, the CG Lock minimises the chances of the child / booster seat couple moving around on the car seat. A similar effect but without the easy adjustability and tensioning could be gained from using something like this once they’re old enough to use a booster seat:
https://www.amazon.com.au/InfaSecure-SafeGrip-Belt-Clamp-Red/dp/B07XY4S31Y/ref=asc_df_B07XY4S31Y/?tag=googleshopmob-22&linkCode=df0&hvadid=712245545733&hvpos=&hvnetw=g&hvrand=2850609866475517956&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1000286&hvtargid=pla-1743109612455&psc=1&mcid=86270975aae1396c9db1abce31c0ff34&gad_source=1
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