I am considering donating shares of an SCI (real estate company) to my children. Does this donation fall under the urban pre-emption right?

No. The urban pre-emption right allows public authorities (municipalities, local communities, etc.) to substitute themselves for the buyer or donee in the case of a transfer of property, such as a sale or donation (Art. L210-1 et seq., Urban Planning Code).
Exception: there is no pre-emption right when the donation concerns SCI shares jointly held by parents and children (Art. L213-1-1 Urban Planning Code).