Ireland to Maine

Can't disagree with you about issues on recently surveyed boats, but I disagree about warming it up with 100 hours of cruising in circles. That's almost 1/3 of their transit. Murphy's law pretty much precludes them breaking down close to help no matter where they're cruising so they might as well have it happen along the transit. At least they won't have wasted the fuel. Also if I break down, have spares and am able to fix it, I'd prefer it to be far away from any coastline I might wash up on while I'm making the repair. It does reemphasize my suggestion of running with another boat though if possible. It also gives me another thought about the longer southern route. If they did break down would they want to be in the northern Atlantic with it's current and wind pushing them east and the weather up there or would they want to be down in the warmer waters and being pushed westerly. By Ken's calculations the first leg would be your shake down cruise, and they could always turn east should they need anything like a yard or medical evac. You know, were it me, I think I might leave that choice up to whether I was cruising with another boat. Southern if alone, northern if with another boat and they'd prefer the shorter route. Especially since the OP said money and time weren't a factor.

Not just another boat, a flotilla. Departures and routes all over.....:

https://www.worldcruising.com/arc/event.aspx

Not sure if dates would work for you....

https://www.worldcruising.com/arc_europe/arceuropeitinerary.aspx

Good idea, but they left their sails behind and they're going the wrong way. But that may have some networking potential.

The DIRONA blog is very well done, and will give you a lot of very good advice. A good shakedown is definitely worthwhile, as I bought an eight year old lightly used 43 foot Nordhavn, surveyed her successfully, performed the survey recommendations and more , then ran the boat to Maine from Florida with professional crew, and had the most difficult trip of my life. The boat is now fine, but she needed that shakedown, and I am very glad I was within 100miles of the coast at all times.

I wouldn't take that crossing without 4 people that can stand a watch. I've done many overnight/long trips (nothing of this many days non stop), and while you can do 2 overnights in a row with 3 crew, any more than that and it really takes a toll. 4 it is comfortable and liveable.

I've always found that with cruising couples they tend to do what they feel like at the time, cover for each other and fall into a rhythm that works for them. Not like professionals doing set shifts.

That's true, but in a trip like this, you simply cannot do it safely with 2 people on a boat this size. I've found with couples, they break a lot of safety rules and somehow get lucky. You cannot maintain proper engine room checks, fix something on deck if something breaks, snaps off and is doing damage to the vessel and needs hands on deck to fix, maintain a proper watch 24/7, and stay fresh, alert, and not fatigued. There are a lot of daily activities that have to be done on a trip like this, aside from engine room checks etc. Making water, pumping out holding tank, fuel transferring, calculations, cooking, re-provisioning the refrigerator, and on and on. If there is any sea state, it's very hard to get any decent or real sleep. For safety, you have to man a watch 24/7, not that sailboat crap where they just leave it on autopilot and go to sleep for hours on end and hope nothing happens. If you wake up to a situation, flooding, fire, etc. because nobody is on watch. You're basically ditching the boat and in a liferaft because by the time you wake up to it, it's too late.

I do a lot of long trips running 24/7, usually for just a night or two, but back to back, do an overnight, pull in clear customs/eat/fuel/get the boat clean/ sleep/ then the next day leave and do an overnight again, and again and again. Everything has to be checked and correct. For example I recently took a 62' MY to Fort Lauderdale from the Panama Canal. Leg 1- 220 NM, Leg 2- 400NM, leg 3- 310NM, leg4- 350NM, leg 5- 155 NM's. Ran at cruise 1st and and 5th leg, we only had the range to run at cruise 220NM MAX in the tanks, cruise speed 22 knots, I carried an additional 220 gallons in drums, but takes an hour at hull speed to transfer the drums. Leg 2 was 48 hours at sea (2 nights), leg 3 was 22 hours at sea, leg 4 was 24 hours at sea. We spent 1 night at a marina after leg 1 and 2 and with a crew of 3 total were all totally exhausted and beat. Luckily we had to wait for weather after leg 3, so spent 3 nights in Isla Mujeres.

Many hands make light work, sure, but couples (and solos) are cruising all over the world and doing multi-day runs. Many on sailboats where sails and course require constant monitoring and adjusting. The OP's are among them. They're not newbies. From post #11 "Hubby and I used to own a 47 ft. Robertson and Caine Leopard catamaran. We are blue water sailors and both have our 100 ton captains licences. We are used to long passages ---- Average at sea time 6 days."