Hi Nic,
We have combined our 10, 20 and 30 year reunions for the past 3 years. It brings the costs down for catering etc and works quite well. I find that each cohort is different when it comes to numbers. Sometimes we get more from the 10 year cohort, sometimes more from the 20 year cohort. My other advice would be to ask the Alumni themselves to see what they want. All the best – Liz