Two clarifications to my earlier post, and then an answer to Waterbird's question.
I am fairly fast among solo canoeists. It is true that, with a canoe and a kayak of about the same length and about the same stability (given the difference in seat height), and assuming that both paddlers are giving the same effort, the kayak will usually be faster.
Your decision to paddle with someone depends more on their skills and judgement than on their boat, but the boat does matter. I disagree with those who said that an open canoe can handle everything a kayak can handle. If steep, four-foot waves are dumping onto the bow of your boat, you need a deck, not a fabric cover (and a strong deck, too -- not every kayak is strongly built).
As to what makes a safe yet fast canoe:
It sounds like speed isn't a huge issue, so I recommend a boat between 28 and 31 inches wide for most people. A 32-inch-wide solo is probably for big guys. Under 27 inches is getting into race-boat territory. A wider boat (probably a tandem paddled solo) usually gives the wind a lot of surface area to push against.
Length doesn't matter much. I would prefer not to go below 14 feet, except for a small and skilled paddler, but you would be surprised what a good 13-footer can handle.
No opinion on depth. Probably any boat chosen for an ambitious trip by an experienced canoeist will have a good depth. Deeper means more windage but also more dryness.
I wouldn't take a flat-bottomed boat on a high-risk trip, but as to the differences among non-flat bottoms (shallow V's, elliptical arches, and so on), no opinion.
No educated opinion on the sit-vs-kneel question. I kneel in rough water, but I have a boat made for kneeling. I have seen sitting canoeists take some impressive waves.
If you find out what model of boat your friends are paddling, you can post the model name here and get a gazillion opinions about it.
Flotation is important. I mean good-quality float bags secured with a "cage" of cord, not just cord through the grommet holes (which like to rip out at the worst possible moment). A pump is very useful, because...
Rescues can be done basically like a boat-over-boat rescue in a kayak. (Get perpendicular to one end of the capsized boat. Turn it upside down, then lift your end so water flows out and away from you. Flip it upright.) Because of the open top, the final flip scoops up some water that a decked boat doesn't get, so you end up with more water in the boat, unless you have a second person who can lift that end.
A few canoeists can roll a canoe. I cannot. That's one of the reasons I avoid high-risk paddling.
Don't assume that practice with rescues on flat water gets you ready to do rescues on bouncy water. Even holding on to the capsized boat can be a challenge.
I don't know what you mean by "ocean conditions," since the ocean can hand you some really horrendous conditions, and of course it depends very much on the weather conditions on the day you paddle. Some conditions will overwhelm an open boat regardless of the paddler's skill, and some (worse) conditions will overwhelm any kayak. Basically, I recommend you practice and paddle together, and then you assume that moderate conditions will present only slightly more risk to a canoeist than to a kayaker; heavy weather significantly disadvantages the canoeist.
You mentioned you are concerned about wind, which is valid. But some of us canoeists eat wind like it's donuts. Just depends on the paddler.
Good luck with your decisions, and happy paddling!