Depends where exactly … we always tended to go a bit further North as a base (towards Royan) at this time of year as you find you might have to follow the weather using Meteo France … and prices are more reasonable.
We tend to plan 2-3 days in advanced using the meteo app… and then you have 4-5 micro climates so you can avoid rainy days that can plague the Gironde this time of year…
Also I guess for me the cottage is EITHER on the beach or a drive to the beach… if the drive is 15 minutes or 5 parking likely takes longer so I find more reasonable places with a 15-30 min drive.
With the kid this gives us a range from the Zoo de Palmyre at one end to the Dune du Pilat at the other… with trips to places like St Emilion etc.