I don't recall many options in Holyhead to be honest. I did the Travelodge when I was there in 2008, but it might be worth looking on Hotels.com for other places. That or maybe look at somewhere around Bangor?
ALR advice, ooh I haven't done that for a while! Most of my advice is normally aimed at a Standard Class ALR, but as you're on one in First stocking up on supplies in advance is less of a concern.
I do have to ask why you must do the WAG-Ex in both directions. It's a nice run, granted, but forcing yourself to be up for the 05:33 back out of Holyhead after getting there late evening may not be entirely enjoyable. Also worth noting the 67 will be at the Standard Class end, which from memory will be at the front on leaving Holyhead, so you don't normally get the benefit of being closer to the engine if you're in First. There have been occasions when the service in either direction has been replaced by a DMU, it's not common but it does happen.
So back to advice. Always aim to have a backup plan, a get out of hell option, just in case something goes wrong. I see you're being sensible and allowing for a flexible itinerary which, as you say, allows one to take advantage of the freedom the ticket offers.
Other advice would be not to under-estimate how tiring long days can get. I packed in a LOT of travel with my 2011 7 day ALR, and by Day 6 I was exhausted. Thankfully in 2012 I learnt my lesson and booked hotels every other night, using sleepers on other nights. It makes the trip more expensive, granted, but oh so worth it to be able to put your head down and grab some proper sleep!
If you're a coffee addict like me, then don't expect anything all that good with the complimentary coffee in First Class. Certainly don't expect a decent size serving either! I usually advise to take advantage of loyalty cards at coffee chains to anyone doing an ALR. It all helps after all!
I would also not under-estimate how hungry lots of travel can make you too!
Finally for now, yes the food is chargeable on top of your fare, but if you get the chance reserve a seat on a GWR Pullman dining service. Extremely pleasant way to travel and dine! From what I've seen it's gone posher since I last did it in 2005, but you'll not get an experience like it anywhere else in the UK!
