If the napkin is cloth, it should always go in the lap of the person (allowances are made for children under the age of 2 - especially when spaghetti is concerned!) <img src="/images/graemlins/wink.gif" alt="" />
There is no real rule on paper napkins - just keep them handy!
Elbows should never go on the table - long standing rule.
Feet kicking - if little one's feet do not reach the floor, the best thing is for them to place them on the rungs of the chair (that is what they are there for - as well as stability) or to cross them at the ankles. They should really not kick - but it is so hard for little ones to stay completely still at a dinner table! I say if they are behaving in all other ways, they are not actually kicking anything or making noise with their feet - let them swing away! It gives them the chance to get a little bit of energy out. However - if this is likely to "ramp them up" then go ahead and put a stop to it. - You know your kids best!