Hi we just booked an all inclusive 2 bed aptmt in Insotel Punta Prima (resort not the prestige suites as suites already booked and apparently have less floor space in them than the resort rooms according to Sovereign agent) for the 2 weeks before your date through Sovereign as it accommodates 5 people and flight time is 2h25 from Gatwick. We haven't been there before but looking at Tripadvisor it looks like it has a wide range of activities that cover children, adults and OAPS. Plus the local area is meant to be attractive and can potter round harbours etc. This resort is also available through Thomson but flights leave earlier in morning with them. Be quick if interested as we found that places for 5 people were pretty thin on the ground.
Last year we went all inclusive to Adriana Beach Club in Portugal in May with Thomas Cook and that was fine, less activities but the children liked it(they were then aged 6,6, and 8). A bit more limited for us adults but lovely beach. There were many groups there like yours with a spread of generations.