Last year for Christmas day we had the privledge of having our missionaries for the whole day. They had the opportunity to email their families early in the month on where they would be and they brought any presents sent to them here and put them under our tree. It was absolutely awesome, Not only spiritually but as a family we grew. We got each of them a set of writing paper and matching envelopes and enough stamps to use on them, and an address book (to write their favorite families in) lol. It was nice to have a fuller house on Christmas morning and I am pretty sure that the missionaries enjoyed it also, especially when one of the elders had just came into the mission field Thanksgiving week and one of the sisters had arrived in our area the week before Christmas.
There is an organization in our area called "Heart House" they help throughout the year and not just on Christmas. They provide food, clothing, toys, even temporary shelter and will help a family get back on their feet and out on their own again by helping to find housing and pay a deposit and or first months rent. This might be the kind of organization you could check out in your local town to donate your items to.
Giving a list to the missionaries of what you have or asking them what families are in need is an awesome idea since they are the ones that have the most contact with the members.