Get a letter from the Bishop explaining these are CHARITY items & therefore you are NOT to pay any taxes on them. Try to ensure HE - or his assistants - are there to meet you at the airport. Get your local Consular agent (American is Bill Kirkman, British is Jenni Mendez, Canadian is Tim Hall) to sign a letter saying these are charitable donations too if possible.
Nice little touch, get the press to attend & then if customs start asking for money, you can show the press how customs deprive the children of basic amenities for school etc!!!
Good luck - Grahame.