Of your list, I am most familiar with Alden and Harlow, Loyal Nine, and Oleana. It’s a tricky call for me, because Loyal Nine is my favourite restaurant, but I think I would have to steer you toward Oleana for your ‘big’ dinner.
Admittedly, both Loyal Nine and A&H have better cocktail programs than Oleana, and Loyal Nine meets your criterion of ‘local’ better. A&H got - and deserved - ‘Bon Appetit’s’ best new restaurant; but while it is excellent, it’s also very much of the New-American trend that you said you have plenty of in SF.
But Oleana is… special. Ana Sortun makes magic happen. For ordering, I would strongly recommend that one of you get the five-course vegetarian tasting ($40), and then augment it with whatever else appeals to you from the menu. That will give you the best chance to experience the menu. I second the advice to try calling for a reservation and/or turn up before they open to wait in line. If you’re one of the first in the line, you’re likely to get a seat at the bar.
Personally, I don’t feel that Oleana’s desserts are as strong as their other food. If you want something sweet after, you could walk a few blocks to Inman Square to Christina’s Ice Cream. The same people own both the ice cream shop and a spice shop a few doors down, and they integrate a lot of the spices into the ice cream flavours (all made in-house). In a city full of very good ice cream, Christina’s is extraordinary.
As to Loyal Nine, I would strongly urge you to consider going there for your smaller meal. It’s mostly small and small-ish plates, so you can try a few things. My favourites are the fried soldier beans (the best bar snack EVER), the fresh cheese, and the molasses ribs, but they do great stuff with local seafood too. They also do all their own baking in-house, so the bread and desserts are fantastic - the chocolate brewis (bread pudding) is a stand-out, and enough for you to share. They also have Frederick Yarm on the bar, who (literally) wrote the book on cocktails in Boston. He and his team do fantastic work. Definitely try to sit at the bar there, even if you have to have a drink and wait for seats.
If you don’t feel up to dinner at Loyal Nine, they also run as a cafe from 8:00-4:00, with lunch (weekdays)/brunch (weekends) from 10:30. Their coffee and baked goods are so great, and their brunch options have been excellent recently. Loyal Nine would also be a good back-up plan if you aren’t able to get into Oleana, since it’s only about a 15-minute walk away, but I love it so much I can’t only offer it to you as a second-choice.
Regina’s: you could get a slice, but you’ll have much better results if you pull up a chair at the bar and share a small pizza between you. Keep it simple - go for cheese and at most one other topping - make sure to ask for it well-done, and keep the bottle of chili oil close at hand. For slices, try Galleria Umberto’s Sicilian-style… if you can get there in time. They make what they make, and they sell out when they sell out. (Also, only go to the original Regina’s on Thacher St. in the North End. Don’t even bother with any others.)
Cannoli: Even if you plan a shoot-out, don’t waste your time on Mike’s: they pre-fill. Modern is my favourite, and they also make excellent sfogliatelle (hard to find) and lobster tails. Maria’s cannoli are good too, but I prefer Modern’s.
Another option to consider is Island Creek Oyster Bar. While I personally feel that Neptune Oyster is superior, it is logistically tricky in that they don’t take reservations and the wait can be more than an hour even at off-times. (They will take your phone number and call you when the table is ready, so you can walk around the North End, but you have to be ready to drop whatever you’re doing and rush back when they call.) But Island Creek does take reservations, and they do some interesting takes on local seafood; and should you need to wait, there’s amazing cocktails at the Hawthorne right next door.