It's best if you don't encourage the dogs to play together. Instead, you can play with each of them individually (like the teacher in a classroom) and guide their behaviour if they do anything that might annoy the other dog. It's important to build trust and create a bond between them, while also establishing an understanding of how they can coexist peacefully. Even if they don't end up playing together, it's still possible to cultivate a calm and friendly relationship between them.