All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
A fiancé, before conducting the marriage contract with his fiancée, is a marriageable man to her, so he is not permitted to be in seclusion with her or talk to her without a need, let alone asking her about things like those mentioned in the question, and she is not permitted to inform him about her menses date. Being a fiancé does not permit him to speak in that manner. However, you may have the marriage contract conducted first and then sometime latter, the marriage ceremony can take place. Once the contract is conducted, then and only then, can you suggest to him changing the wedding night.
For more benefit on the relationship between a fiancé and her fiancée, please refer to Fataawa 81356 and 81668, and to Fatwa 99391 on having sexual intercourse on wedding night.
Allaah Knows best.