tell dh not to put the money up (even if he were able to attend). it can be a major no-win proposition.
i planned (very small committee of a few friends) our 20th reunion and found that while there are tons of people who assured us that they would attend when it came time to get tickets bought it was a whole different ball game (oh, i can't pay now-can i pay at the door, oh my god its' going to cost that much, wow i did'nt realise hotels in our hometown cost so much now...). we based our planning on the responses we got over several repeat mailings (size of the hall, menu) and ended up with a huge deficit (and this was not a huge over the top, mortgage the house to pay for tickets event) mostly because the hall charges for the room or has a minimum number of meals. if you don't get that number of attendees they don't lower their charges (and changing a venue can result in losing a deposit plus paying a higher charge for securing another location/caterer on short notice).
we were lucky-we used a reunion company that fronted all of the money (there was a minimal per person charge tacked onto each ticket price to cover their expenses). but that company lost money (and must have had repeat experiences cuz they are no longer in bsns).
we learned later that 5 year (and in the absence of a 5 year-10 year) reunions have the biggest turnouts (our 10 year still holds the biggest single night bar proceeds at a local elk's club

). after that it's mostly the biggies-20/30/40...
we did'nt have a 25 because i was unwilling to take it on, and despite loads of people with "great ideas" noone else actualy stepped forward.
oh-and as a side note if he decides to stay involved, one of the biggest money losers is the concept that the "reunion committee members" get in free. you will lots of volunteers who do nada to achieve this perk (the company we used only gave comps to us if we achieved a set number of attendees-and then it was limited to a set number).