hikrchick

Hello!
I'm ready to post our first attempt at an itinerary for our 2-week trip to Wales, 22 June-6 July. This is our narrowboat/ Mon & Brec + hiking trip, and we will be renting a car for the second half after we get off the boat. I welcome any advice, including suggestions on Cardiff hotels. We've got the flights booked, the narrowboat booked. Now I need to do all the hotels, which would be 2 different hotels in Abergavenny, one in Hay, one in Cardiff, and then Premier Inn King's Cross the night before we leave.
21 June, Friday: Depart EWR.
22 June, Saturday: Arrive LHR, train to Paddington, then train to Cardiff, and then train to Abergavenny. Overnight Abergavenny (somewhere).
23 June, Sunday: Walk and stretch in Abergavenny. Waterstone's to pick up something to read. Overnight Abergavenny (same place/somewhere)
24 June, Monday: Abergavenny Waitrose in morning to pick up food for the next 4 days. Then taxi to Gilwern to pick up narrowboat, I think we can get it at noon. Overnight narrowboat.
25 June, Tuesday: Narrowboat. Overnight narrowboat
26 June, Wednesday: Narrowboat. Overnight narrowboat
27 June, Thursday: Narrowboat. Overnight narrowboat.
28 June, Friday: Return narrowboat at 9 a.m. Taxi to Abergavenny. And now it is all options and I'd love some pros/cons either way. Option 1: spend the day in Abergavenny, stay overnight in Abergavenny and go on Saturday to Cardiff Airport to get the car. Option 2: right away take a train to Cardiff, then out to Cardiff airport, pick up car and return to Abergavenny to stay overnight. Option 3: take a train to Cardiff, out to Cardiff Airport, pick up car and drive out to Hay to stay overnight.
29 June, Saturday: If we've stayed overnight in Abergavenny without getting the car, then we would take an early train to Cardiff Airport to pick up the car and then return to Abergavenny OR go to Hay. OR if we did that the day before, leave Abergavenny OR already be in Hay.
We have 4 1/2 days, through Wednesday July 3 (overnight somewhere). We would like to split these nights between Abergavenny and Hay to be able to walk in two different regions of Brecon Beacon. Either we stay in Abergavenny and go to Hay later in the week, or take the car and go right out to Hay and then come south to Abergavenny, which might be easier on 4 July to return the car to Cardiff airport.
4 July, Thursday: Drop off car at Cardiff Airport in the morning, taxi to Cardiff. Explore Cardiff. Overnight Cardiff (somewhere)
5 July, Friday: Mid-morning train from Cardiff to London. Overnight London, most likely Premier Inn Kings Cross that I still have to book.
6 July, Saturday: Tube to LHR and depart at 1 p.m.

So, the immediate question is, thoughts about picking up the car at Cardiff Airport on the Friday June 28 after getting off the narrowboat, or waiting until Saturday to get it. If we pick it up on Friday, do we stay the next couple days in Abergavenny or go out to Hay and then come back to Abergavenny a few days later.
I'm grateful for any suggestions, I am super-flexible at this point with (most of) the plans!