Shops are close on Sunday and Monday morning, Uffizi and Accademia and some others museum are closed on Monday and May the 1st .  Although US$ and credit cards are widely accepted, to have some cash Euro with you will be convenient. 

Tuscany is generally a safe place, take only the traveler’s due diligence. 

Carry your mobile phone with you, could turn out to be useful to keep in touch while on tour.