Ultimately this is your decision but, as you say who is this? What are they offering submission to me comes within a loving relationship, you want to just have sex then fine, but for me bdsm is more, providing more for both parties that are involved.

I would question the motive behind this and the speed, to meet in a stereotypical romantic place is kinda misleading for me, to abandon your knickers ok fair enough carry a spare but I could take this as acceptance they would be discarded.

Considering the available information this person has thought this through and sounds extremely keen to meet, so then work through it, prove the worth before you commit, others could suggest go for it. Just be sure of your choice and stay safe. But be happy and enjoy.

So in answer to your question, sorry cliché ask questions of this person.

Sett