We built a deck on our house in 2001 after the previous one all but collapsed. It was rather old (20+ years) and we could almost pull it apart by hand
It was also shaped inconveniently around the area where our pool is, so we rebuilt-reshaped everything to work better. We also needed rails to prevent the kid from wandering out.
As far as post holes go, decide if you want holes or you want concrete post pads first. The pads are nifty, weigh a ton and keep the posts out of the ground so there is less likelihood of rot at the base. We actually buried our cement pads after putting the posts in. The pads are pretty cheap, probably $5-10 each and really help stabilize the deck. If you're adamant about post holes, use a post hole digger. Better yet, get a tube and sink it in the hole, pouring in concrete after. The cement pads are the same concept, just easier.
Use 2x10s for the frame of the deck, well worth the additional cost for the return in strength you get. Probably won't add to the longevity, but won't detract from it either.
Measure twice, cut once and use a level every single time you attach something
. Use screws, not nails. Nails pop and tend to rust more easily. Replacing rotting boards down the road is much easier with screws as well, just reverse the drill. A whole lot better than using a crowbar to pry up a rotting board, damaging the surrounding boards at the same time. I think we used 3 1/2 or 2 3/4 inch screws for putting it together. I'll try and find the spares at home to answer your question.
Inspect the wood, don't let some home depot give you a bunch. If you get a warped piece, take it back. It's defective and a pain to them, but you are paying a premium for flat wood. Also use pressure treated wood if you are still able. Copper chromated arsenic is an evil thing, if you listen to the environmental working group, but your kid would have to ingest 2.5 ounces per day
for life to get the chronic dose that might, just might lead to cancer in about 50 years (never mind the confounding factors they'll face in the interim). I know Minnesota is not exactly the hotbed for termites, but carpenter ants can do their fair share of damage too.
Dork my ass