1. Get a startup attorney (you probably already have one, who incorporated you, if you don't - use one of the bigger names (wilson sonsoni, gunderson, cooley))
2. Figure out what your perfect offer would be, and counter
3. Rule #1 of any negotiation is to be willing to walk the fuck away if you're not happy. As soon as you become a little desperate, you've lost leverage.
4. I'm not quite sure how double trigger acceleration works but if you're getting options that vest, you could potentially figure out a way to get all (or some) of your options accelerate if you do get terminated. Usually this applies only on change of control, but I'm sure your attorneys could cook up something.
5. Why do you need to get acquired to work on the million ideas for the future? Have you thought about raising capital to do that (you know, the choice that Foursquare took when it turned down acquisition offers) - raising capital when there's already acquisition interest should be easier if that's the route you want to take and you can take money off the table if you need the cash and still build a potentially massive company. Talk to VCs anyway. This goes back to what you think the size of your opportunity is and how tired you are of going after it.
6. If you do "verbally" accept the offer, make sure you and your attorneys go over the LoI and terms with a fine tooth and comb, you could still get screwed. There's a million ways that could happen and that's where good attorneys will help.
7. Don't panic.
8. Best of luck!