Help! travel in holland..staying at nunspeet, hotel dennenhoeve.independant day on a sunday..public transport?

we are going as part of a coach trip to see the tulips etc and have decided to 'go it alone' for a day.sunday 15 april. i would like to take my wife out somewhere interesting, maybe amsterdam direction..is the flower market open on a sunday?what is the situation regarding trains..it looks like the train station is fairly close to the hotel so is the obvious choice. do the local networks have a 'rover ' style ticket for train tram bus networks? can anyone recomend a 'must see' venue? we've been to the red light district and the c trips and the museum etc. thanks.