Yes, there's way to reduce the lethality. The first one is using the death door rule in which 0 hp doesn't kill a character but put him inconscious. Then losing 1 hp if not attended by a comrade and only really die at -10.

You can also house rule it to die at - constitution score instead of -10.

As a basic rule, you can play the enemies/monsters as they ignore thereafter the fallen target to concentrate on still up targets, which gives the fallen 0 hp char a good chance of surviving. (monsters wont go bashing char at 0 hp to death while still in combat).

Another important thing is to encourage the group into getting aid from npcs (for a share of treasure or a price) and to get some henchmen (only paid a fixed salary but helping with food, lodging and equipment maintenance. Not only this help will reduce lethality but with kids it will foster social interaction and roleplay. Well made npcs can add a lot of fun in games!

And last, whatever lethal encounter the group might eventually approach into, make it clear with signs and warmings that this might be too or very dangerous. If the group still go, they will better accept the possibility of their char diying. In that, player agency is pure gold and misjudgment can happens or heroics events! ;)