The Rambam says that it’s better to give less butt more often than more but less often. This is just to instill the Midda of giving in yourself. The Mitzva, however, is accomplished either way.
In fact, the Maharal argues with this Rambam and quotes a Braisa that all Tzedaka that a person gave throughout his lifetime gets added up into one large sum. So we see that this Mitzva is different than all others in that the amount matters and not the act.
Being nice to the guy is called Gemilas Chasadim; Tzedaka is to give money. I wrote earlier to have the bulk done by the bank, to make sure it gets done right – which is most important, and to keep some small change to give out. This way you are Yotze both Shitos.