I'm sorry to hear that

At least if you have to bury them, you know that they're gone and what happened to them.
We have had to move without cats sometimes when they went out and didn't come back, and I always wondered what happened to them, were they hurt, were they locked up and came home when released only to find us gone? I had one cat that was locked in someone's shed for 2 weeks before she finally made it home. Another cat "disappeared" when we were about to move once. Our neighbour hated him because his wife let their bird out once and it came into our yard and our cat got it. My husband and I have always believed he caught the cat when he knew we were moving, and did horrible things to him

That guy was a nutcase and his wife left him around that time because he couldn't stand her being out of the house or talking to other people.
Anyway, yeah, it's hard to bury them, but that would be my preference, because you have closure.