A guy has offered to take me to the museum and to dinner. This will be the first time we meet after a few e-mails between us. He suggested meeting at the museum at noon but then assumed that we will eat around 8 or 9 at night. How much time should you allot for a first meeting with someone you only know from an online dating profile?
You're setting yourself up for disaster. You said you've exchanged emails, but have you spoken on the phone? Never meet someone without first speaking to them several times! The first date should just be coffee or drinks. If you like each other, you can then progress to lunch or dinner. If you don't, you're free to leave. Committing to a museum and dinner is just too much time to spend with someone you don't know.