The aim: a human approaching is no longer a threat, but the announcement of a bonus.
An abundance of resources
Multiply the toys and points of interest. The less rare the object, the less need there is to defend it.
The passing "Jackpot"
When they have an object, walk past at 2 m without looking at them and toss an ultra-tasty treat on the floor. Carry on walking.
Systematic swaps (trade-up)
Offer an identical toy or a higher-value treat. As soon as they let go, say "Bring it!" and give back the original object + the bonus.
The treat trail
If they keep an object, throw a trail of treats as you move away. While they eat them, calmly pick up the object, then give it back + a bonus.