You won't need much down there. Comfortable shoes for walking around the farms, couple pairs of shorts and tee shirts, maybe a light coat/hoodie and a pair of pants in case it gets a little to cool for ya at night. They cover cigars so you don't need to bring many, but I brought about 15 of my nicer non-DE smokes to share/smoke. I brought back about 20 smokes that they gave us (samples & blending session cigars), so make sure you have some extra room in your suitcase. Some of the guys brought beers down with them to share, but there will be plenty of booze and you can always pick up a bottle or two at the airport when you arrive in Managua. Have fun!
Forgot to add, the thing I was most glad I had was the charging case for my phone(iPhone). Being able to double the battery life was great considering I was only able to charge the phone at night. I took a lot of pictures down there with the phone, plus watching movies on the 2 flights.