Historically in the past we have seen all the major IT holiday charter airlines use on their prime high density routes big wide body aircraft - all big people movers.
BOAC used their new 747-100's LHR to Palma at weekends when they first got them from 1971
Then Court Line Tristars Laker and BCAL DC-10's, B-tours Tristars
A300's of Laker Monarch Orion Dan Air.
Britannia 767's from 1984 and so on
In Europe Condor Scanair/SAS KLM Sabena LTU Finnair Martinair TEA Conair used a mix of 747's DC-10's A300 A330 MD11 and Tristar to the Med and Canaries all the time.
Since the plethora of new 737 and A320/321 coming along we have seen smaller and smaller aircraft used on peak IT routes with ever increasing design in maxing out of seats - the 757 and 767 are now a rare species.
The economics and size of the A330 see's their use again on peak IT routes
The 787 which TUI use around their short and medium haul does not have the same economics and they were not really designed for short haul use.
Not sure if we will ever see the days of large numbers of wide bodies back on these types of flights