Welcome to FlyerTalk, blishwalt

Considering your Avios balance, I am guessing you’re looking at an economy class redemption which for LGW-SJO is 32,500 Avios (off-peak) or 50,000 Avios (peak) per person (round trip).

I can see cash fares starting at £590 p/p for travel in World Traveller. A BA redemption booking (when/if you find available seats) will save you money against the net fare (approx £300) but you’d still need to fork out an additional £290 per adult and a little less for children due to recent changes in the way UK Air Passenger Duty is now assessed. For this reason, booking long haul economy class redemptions represents very poor value for money.

You may wish to consider paying cash for your ticket and using your Avios to upgrade from WT to WT+. The £590 fares book into N class and are eligible for upgrade using Avios.