We are also going on the caribbean cruise on the 16th April. The last two years we have flown to Barbados and sailed back to southampton We found the weather amazing only two days after Madeira did it turn colder and sea was not rough at all. We imagine it will take a day after our stop to vigo to warm up and a couple of days after madeira to cool down Hope this helps see you on board!!
I'm not sure of your itinerary but if you are going south via Canaries and then across you should have warm to hot weather from Tenerife on. You will probably get some rain in the caribbean at that time but it's over fairly quickly and usually it's warm rain. Go on the net and look at the weather sites, they will give you a history of average weather conditions for each time in the year and for all your ports of call. Ida Dow.