In spring, the south of France/NW coast of Italy is great, particularly near Easter. Start in Menton, which is lovely, plus they have the lemon festival -- strange and fun!:
https://www.fete-du-citron.com/
If you can do fall, there are far fewer tourists on the SW coast of France/NE coast of Spain at that time, and the waves are really picking up if anyone in the family surfs (this is all my kids think about so it drives our vacations). The food is great, there is a street art festival in Bayonne, a film festival in Biarritz and plenty of fetes to keep you busy on weekends all over the Pays Basque in the Sept/Oct timeframe -- specifically the fete in Espelette which is awesome.