For reasons of time-saving and avoiding retie figure 8 knots all the time, can I clip the figure 8 knot via two carabiners each clipped to either loop of the harness? This way there will be no cross loading of the carabiner. Clipping is way faster than tying figure 8 knots.
The carabiners are double-locking ones.
First, thanks to all of you. You provided such an amazing info! Can't stop clicking upvotes. I see there is missing some clarification about why I need all that. So I'm putting it here.
Soon I with my kids will go to a hiking trip involving several sections of scrambling through a canyon. The youngest is 4 y.o. I have harnesses for the elder kids and full-body kid's harness (Black Diamond Momentum). Since we will have several such sections of climbing and regular hiking between them I thought that clipping and unclipping carabiners would be much faster (mind the fact that I will safeguard all three kids). The scrambling sections themselves are not very long, so they will not take much time to pass. There are anchors on top of each section, so my plan was that I climb, clip the rope, then probably go down and safeguard my kids one-by-one (there will be more adults).
There will be no hard falls, since I'll watch them and will keep the rope tight through my belaying device. Having that convenience of fast clip/unclip is hugely important and also safer. Because if you stuck there after sunset - it's no joke.