What can I sow now to plant in raised beds later?

Hi folks. I'm new to this forum and to vegetable growing in general.

We're currently in the middle of constructing some raised beds - they won't be ready for two or three weeks. I'd like to start growing stuff to plant in the raised beds once they're ready. We have a greenhouse, so I can start things off in seed trays.

I was wondering what would be a good choice. Some seed packets say to sow them where they're going to grow. Is it possible to sow in seed trays instead then transplant the seedlings?

Any suggestions/advice welcome!

You can start winter caulis & sping cabbage for later planting out - but DON'T start them in the greenhouse, it's way too warm. Mine are doing fine in seed cells on the patio.

Here's a sowing/harvest guide:

Sowing and Harvest Chart