Hola
The time you are waliking in will have fewer pilgrims on the road and in my experience you dont have to book ahead, but I still would book a bed in Roncesvalles and the dinner.
You are arriving late in Bayonne and there might be delays along your way, so I would say; take an extra day.
Book a bed for the night in Bayonne and the 22 you take the train to Saint Jean and have a relaxing day there - see the church, pilgrim office, other pilgrims arriving and so on.
Depending on where you are from you will recover from any tiredness from your travel.
Some people who come early actually go for a test walk up the road, just to see how it is
If you start at 8 or so most people wil have no problem getting to Roncesvalles, depending on the weather.
There are two ways you can take -the Napoleon over the mountain top or the Valcarlos in the valley.
Both are lovley and you will have to ask the pilgrim office in SJPDP what they think is the best way. They will advice depending on the weather conditions.
After Roncesvalles I wouldnt book if I were you, but you will know once you start your walk how busy it is and adjust acordingly.
Don't worry too much
Just go slow the first week and for now focus on getting all your gear together and get yourself to SJPDP.
The rest will unfold for you a day at the time on your Camino.
I hope this helps.
Buen Camino.
Lettinggo