The danger with a cracked egg is that the sterility of the contents is compromised and (since chicken-shit is a major vector for salmonella) possibly contaminated by salmonella. Salmonella doesn't reproduce so well when frozen, though, so it would be my personal practice to immediately take the eggs and boil them, based on the following logic:

1. The eggs were intact and sterile when laid
2. They cracked only when freezing expanded the contents
3. Any salmonella near the crack would also have frozen
4. Frozen salmonella does not multiply
5. There is minimal risk of salmonella contamination

If allowed to thaw or repeatedly smeared with fresh, warm salmonella, I might be concerned. If the frozen eggs are immediately gathered and boiled, there simply isn't an opportunity for much contamination, QED.