Actually, Julie, things were pretty low-key and boring in 1961, JFK had been inaugurated as president that January but no flower power, hippies or peace signs, and the Beatles hadn't even invaded the music scene. Vietnam wasn't an issue yet, and when it became one that's when the country went into the peace, love and flower-power mode, in the latter 60's. Clothing was still pretty sedate, no bright colors and still reminiscent of the bobby-sox '50's, no smiley faces, no black lights, no hanging beads, nothing was "groovy" yet.
The BIG thing was the space race and to see who could get there first, the Russians or the Americans, and it President Kennedy's pet peeve, he asked Congress for $531 mil to put a man on the moon. BTW, he also told Americans to build themselves bomb shelters, so the prevailing emotion was fear. The Peace Corp was established that year, the first "Six Flags" opened, and Pampers were introduced ; )
Family was still a big thing, think "Leave it to Beaver' and "Father Knows Best."
Popular Films were:
The Guns of Navarone
The Parent Trap (the original with Haley Mills)
The Absent-Minded Professor (with Fred MacMurray)
101 Dalmatians (the original)
Breakfast at Tiffany's
El Cid
The Misfits
The Hustler
West Side Story
Popular TV shows were:
Wagon Train
Bonanza
Gunsmoke
Perry Mason
The Red Skelton Show
Andy Griffith
Candid Camera
My Three Sons
Alfred Hitchcock Presents
The Twilight Zone
Mister Ed (the talking horse, lol)
And some of the popular songs were:
Stand By Me by Ben E. King
Surrender by Elvis Presley
Runaway by Del Shannon
Let's Twist Again by Chubby Checker
Crying by Roy Orbison
Hello Mary Lou by Ricky Nelson (he became "Rick" as he aged)
Introduced that year were:
Total Breakfast cereal, Mrs. Butterworth's Syrup, Green Giant frozen peas, Sprite, Coffee-Mate, Sylvia's restaurant (NYC), Hardee's (fast food chain) and Tang was introduced a year or so before.
Scott Baio, Barack Obama, George Clooney and Lawrence Fishburne were all born that year as well.
Since you have ordered the party supplies and decorations my suggestion is to go with an overall 60's theme, and use DVD's of the movies or TV shows, and music of the year to set the tone, so it all coordinates. All the information I've given is in the sites below, along with much more, especially in the food site, as i didn't know which food theme you'd want to go with, there's several listed.
Sounds like it's going to be a very cool party!!
http://www.infoplease.com/year/1961.html
http://www.thepeoplehistory.com/1961.html
http://tsort.info/music/yr1961.htm
http://www.foodtimeline.org/fooddecades.html#1960s
http://en.wikipedia.org/wiki/Leave_It_to_Beaver
http://en.wikipedia.org/wiki/Father_Knows_Best