I would think that laying a good thinset down and applying your pavers should do, then mortar in the cracks.

If you patio has a crack in it from earth shifting, does this crack get bigger during the summer and smaller during the winter?

If this does happen, the break or crack will transpond to the pavers also. Then this idea might not be a sound one.

Now, are you going to line this fire pit with fire brick? If not, the pavers will crack during heat process. Consider this.