Dan, I am *so* stoked for you guys! I've had an amazing time being a "startup dad" for the past 2 years and I hope you have a similar experience!
There is a quote I've heard in many contexts now that I'll co-opt for my purposes here. It goes like this :
"The best parent in the world is the one having the most fun."
You guys, I've noticed, tend to have fun doing whatever you are doing, even waiting in line for taxing at SXSW. :-) Try to carry that over to parenting. Babies and newborns are like little sponges, incredibly sensitive and perceptive to their environments, so just remember the incredible influence you can have them just with a smile or laugh or your voice.
There will be moments that feel truly overwhelming and even a little desperate (it's pretty amazing how these beautiful little beings can quickly convince you that you are the worst parent ever with their various protests) but I have found that you just have try to laugh at yourself a little bit, don't get too wrapped up in negative feelings and *just keep moving forward* through whatever challenge you might be having. Really, these moments are few and far between, but I think the right attitude can make it easier to get through them.
I've also found that being a parent is an opportunity be a kid again yourself! It's amazing how you can be transported back in time by watching your little one. You'll find yourself really appreciating all of the things your parents did for you growing up. This feeling has been so intense for me that for father's day this year I made this for my own father :
http://www.heythanksdad.com
I guess I could go on for a while at a high level about all of it, but maybe we should do that over a beer!
A couple of specifics. The absolute best accessory we have is this backpack :
http://www.rei.com/product/810852/deuter-kid-comfort-ii-child-carrier
Orion *loves* being in this backpack and the places we can go with it. We live in a place that has amazing walking access to trails and parks and we take full advantage of that. So far I would say we average about 8 hours a week of just hiking around and trails and chilling out in parks, it's the best time ever. Just get one, use it, love it.
The other thing we have picked up (actually two of them now!) is this rocking recliner :
http://www.amazon.com/gp/product/B005RCMAU4/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1
*Super* comfortable with the kiddos for reading, feeding, napping. Ariel loves it because she can be very comfortable for feeding and then fall asleep right in the chair. You're going to spend a lot of time with the kids in arms, so it's worth making sure you have comfortable spots to be.
And of course, I have a couple of apps that are pretty much indispensable. Pandora is of course amazing and really great for the kids.
The best white noise app :
https://itunes.apple.com/us/app/white-noise/id289894882?mt=8
Orion really loves the whole Peekaboo series of apps, they are great, he has learned a ton of words from them. Peekaboo forest has beautiful artwork :
https://itunes.apple.com/us/app/peekaboo-forest/id389240936?mt=8
Alright man, that's enough for now, like I said, I could go on and on and on. But it's best done over a beer. We have a group of Dad's that get together every month or so for "Daddy Hours" so let me know when you are "ready" and we'll get in you the loop.
Cheers!
Jereme