I got home from work this evening and decided I'd better mow the lawn as rain is threatening. While I was mowing, DW came out to bring some compost out to the bin and she checked on the bunny's burrow. They were all gone. Either they were weaned or the mother moved them to a new den.
As I was mowing, one of the baby bunnies came tearing out of an island of plantings in the lawn and made a break for the wood as I came near with the mower. The bunny certainly moved quickly and looked healthy. I guess they must be weaned.