Use puerta a puerta.
My sisters just sent 2 boxes full of food (for their use), used clothes (to give away) and gifts to SD. They paid $70.00 for each box. (moving boxes). The shipping co. come to your house and sealed the box in front of you and deliver it to the address you give them.
I am not travelling this year but this week a sent a tank-$100.00 Quisqueya Shipping-sale. I said food to them but I cleaned my closet with clothing that my children outgrown or do not wear anymore I put them in the tank, also all lotions, perfumes, shower gels that were taking space in my apt., an old Nintendo system and the games, a blower, hair clippers.
I sealed it myself but when they came to pick it up they sealed it with their tape on top of mine. I hope it will get there before my sisters return to NY.
Next time call one of this agencies and tell them you are sending donations. I think you will find one that can accomodate you so you do not have to carry heavy.
Most Dominicans do not ask others to carry for them anymore because maybe they have to tip them 10 or 20 dollars for the favor and for $70 or $75 they can send a full moving box with items for the whole barrio.