Ask HN: Quitting from a small startup?

I've been a key member (first hire) of a small start-up for a couple years but now it's time to move on.

I recently accepted a new position at one of the big tech companies and, to be frank, the company I work for now relies very heavily on me.

I'm the only one with any experience doing front end development and they have a lot of need for that right now.

What are some tips to help soften the blow when I give them my two weeks?

I've got some ideas but I'll let you have at it without influencing the commentary by mentioning my current 'plan'.

Thanks in advance for the tips!

Edit: Just to add, I'm on good terms with everyone. They've been working me to the bone for months now (one of the reasons I chose to leave) but it's been a positive work environment 100% of the time.