That's a tough one Angie. It is so deflating when you plan something and work so hard on it and you don't get the response you hoped for!
I'd suggest taking a look at the timing of your event first. Was it the same as last year? Was something else going on this year that wasn't there last year? Around here it's football.
Next, did your advertising reach the desired group(s)? History tends to attract an older audience. Did you put flyers in senior centers and let local AARP chapters and church groups know about it? It is hard to get the word out to the right people sometimes, especially with a small staff.
Weather also plays a role, and it can work both ways. Nice weather means people might want to do something else with the last nice fall weather OR it might mean they want to get out and come to the museum. Rainy weather often works in our favor, but not if it's TOO rainy and people want to stay home.
We've found that Saturday "drop in" programs are not good for us. We do better with programs where you have to make reservations and we also do better in the evening during the week. Saturday visitors tend to be families, and they don't want to attend history lectures. We just ran into this at our grand opening a few Saturdays ago. We didn't have a good turnout at the talks we scheduled, but the crafts and science shows were busy. So we have decided to stop planning drop-in history programs as part of larger events because it just isn't worth it.
We always pair our history programs with a meal -- either a "Tea with the Curator" where we provide breakfast sweets in the morning or a "Soup at Six" program where we provide a homeade soup, bread and dessert. Another local museum has a successful brown bag lunch program where the participants actually bring their own food and eat before/during the speaker's presentation.
I know it isn't great for morale when a program isn't as successful. And if you have speakers from outside the museum, it can also be quite embarassing!
You have to walk a fine line between taking a risk and trying new things, and falling back on your old stand by events that are always successful.
I hope if you plan to do this again next year, you have a better turnout!