You did not say if it is all adults because some all-inclusive are adults only. We do not have a R&B festival and the Jazz Festival is during the month of January.
http://barbados.org/news_details.php?newsID=66
I highly recommend our annual festival, it portrays our culture. It is the Crop Over festival. That usually starts early in May but intensifies and then culminates the first Monday in August with a street parade. You did not state how long you will be here for but at least two weeks in the month of July and including the Monday in August should be enough.
http://barbados.org/cropover.htm
http://www.funbarbados.com/Crop_Over/
http://www.youtube.com/watch?v=owLBR4Slz4E
http://www.youtube.com/watch?v=IGQSv8Fanx0&feature=related
There are many all-inclusive hotels, these are a few.
http://www.barbados.org/allinclusive_vacations.php
Some others are here including Almond Casuarina which is very near to the night life (St. Lawrence Gap). Included in this is the adult-hotel which is the Club and Spa.
http://www.almondresorts.com/
Check here for travel agents in Maryland.
http://www.planetickets.com/travel_agents/maryland_travel_agency.htm
http://www.marylandinfo.com/Travel_and_Vacation/Travel_Agencies/
You can also book your flight online as well as it might be cheaper. You can also go to the hotel site and book the rooms or just email them and ask advice.
As it is two years away you can just save the money in the mean time. At the beginning of the year you can reserve the hotel accommodation as the hotels tend to be booked very early. Book your trip early too as you might not get any if you wait too late. Have enough money to go to the different fetes(parties) and for drinks.