It is different in EVERY area- in my town a garage sale over Easter weekend would not do well AT ALL. Too many people spending time with their families.
I do have A LOT of garage sale experiance though, because we've done one every year for several years now and my parents also had one every year.
2 day sales are great, In my opinion, BECAUSE...you can do a 'as marked price' sale the first day and what ever is left on the second day could be put down to 1/2 price just to get rid of it.
My family has a 'garage sale rule'...if it goes on the sale IT DOES NOT RETURN INTO THE HOUSE OR STORAGE!!! We box it up right after the sale and bring it directly to good will! So, when stuff is marked 1/2 price the second day, most of it does go.
We always start ours early in the year (so people are just starting up with the 'rummage sale season' and they are EXCITED to get out there and go to as many as possible)...We always do ours on a Thurs. afternoon (starting around 4) and all day Friday. Then after 11am Friday everything is 1/2 price. In our town, it's normal to have sales on a Thursday and or Friday- But it may differ in your area.
I would DEFINATELY say no to Easter weekend, but I don't know what your area is like as far as that goes...