If you arrive in early March, best to start your jouney from Grazalema, especially if you like orchids. The weather might be less rainy in May, but even then it is very likely that you get some showers. There are nice walks starting from the camping site, close to the town of Grazalema, see http://www.topwalks.net/en/grazalema/puerto_presillas.htm
. Another nice place, especially for a 5-years old is Torcal de Antequera. You can take a short walk, some 3 km, in a landscape full of exotic flowers and exciting rock formations, see http://www.topwalks.net/en/torcal/torcal.htm
. In case you want to combine bathing and flowers, visit the Cabo de Gata-Nijar in Almeria, great variety of flowers growing in sand dunes, cliffs etc.
For April, I would recommend the park of Cazorla, Segura and Las Villas, http://www.topwalks.net/en/sierras_cazorla_segura.htm
, nice walks with many endemic plants like Viola cazorlensis, http://www.topwalks.net/plants/pink/viola_cazorlensis_more.htm
and Pinguicula vallisneriifolia, http://www.topwalks.net/plants/blue/pinguicula_vallisneriifolia_more.htm
In May, you could tackle the summits of Alpujarra. In Sierra Nevada, you find so many endemic, absolutely charming flowers. The surroundings of seven lagoons is a great place for flower spotting, http://www.topwalks.net/en/trevelez/siete_lagunas.htm