Merryweather has worked for the Ford Motor Company for 23 years in a range of marketing and sales roles in the UK and Europe.
Van Otterdyk manages a team of professional project, contract and process managers in various media production channels.
ISES UK president Richard Foulkes said: "As well as giving enormous insight to the board in the ongoing growth and development of the association, they will help us understand better the education requirements of the in-house event planning teams across corporate and not-for-profit organisations so we can ensure the society is tailored to their needs and aspirations."
QD Events managing director Fran McIntyre has joined the current board as director for Scotland.
Foulkes added: "Scotland is home to some of the country’s most creative and dynamic events and with the Commonwealth Games coming to Glasgow in 2014 there is a whole host of opportunity for the creative events industry to create, connect and inspire."