Hi wonderful community!
Your guests can write their meal options directly on your website! 
In order to do so, you have to create a poll or survey:
How To Create a Poll or Survey on your Wedsite
The meal option are not included in the RSVP on your website, but you can still add these little instructions to facilitate the process and ensure that every guest answers:
How can my guests RSVP on my website? 4 step instructions
If you have more questions, don't hesitate to ask them here! 