Blue Ribbon March, O'Reilly & Feldstien, is probably the easiest march you can come up with. It is OOP, so you're going to have to ask around if you don't already have it. Spitfire is also a good, easy march (and in print)...but it isn't as easy as Blue Ribbon.

Acropolis
Wings to the Mind
Strength and Honor

Those three are probably your best bet from the list. Dorian Chant could also work...but you have to know your kids as it is not as easy as the other three.

Contrary to popular belief, Dance Celebration is NOT easy, let alone one of the easiest things on the list. There are at least 5 independent rhythmic lines going on in this piece all at once. If you've got sections with issues regarding rhythms, steady beats, and confidence with independent lines...this piece WILL expose you.