Oh, well, I noticed that there's a box in my church that collected stamps and I think someone sells them and uses the money to support missionaries all over the world.
Maybe you could do the same? Are stamps worth more than their face value nowadays? Mine are in a book, they are all new stamps (not postmarked) so I could just give the whole book to the church I suppose. I don't collect them anymore.
Most of my stamps are postally used ones which have no value anymore for postage. Most of them have no real value to those who still collect because the old collectors usually already have them and like me don't need any more duplicate copies. The number of newer younger collectors in the United States and probably in most of the more technologically advanced countries (including of course, New Zealand) is greatly diminished from earlier years. Supply and demand works on stamps values as in other things of value. I have stamps over 150 years old that I could not sell to most people because most people aren't interested in stamps at any price. Those who are usually already have them. I am not meaning to say your stamps are worthless, but to most people they would be. Only serious collectors could give a reasonable value for them and only a dealer would almost always be willing to buy and collection or stamp worth the trouble to him. Giving stamps to church wouldn't mean much to them unless they were still valid for postage (unused) or they had a stamp collector who could set a fair value on them and knew where to sell them.
In the United States the best source for used stamp values are found in the Scott Standard Postage Catalogues which give values for world-wide stamps from the earliest issues in every country in the world to the date the Catalogue was published. New sets of catalogues come out every year with values shown in U.S. dollars. [They are expensive costing $80-$100 U.S. dollars per volume. The world is covered in a six volume set.}
While Scott includes New Zealand stamps in its listing the Stanley Gibbons Stamp Catalogues based in Great Britain may have a better listing with the values shown in British currency. I am not familiar with a Catalogue based in New Zealand, but there may be one. There are certainly stamp dealers. If you know an honest dealer, he may honestly tell you your stamps are worth less than paper, but even if he were to offer you money for them, it would be unlikely to a lot. Stamps are usually sold at a fraction of what they are listed in catalogue. Catalogues will have separate price listing for used and unused stamps. Scott stamp #1 for New Zealand pictures Queen Victoria was issued July 20, 1855 printed in London and the Scott value for unused copy is $75,000.00 while it is only $21,500.00 for a used copy. Those prices, of course, are for stamps in good condition.
The oldest New Zealand stamp I own is Scott #37 a used stamp issued between 1864 and 1871. The latest Scott Catalogue shows a value of $135.00. My stamp has the same picture of Victoria as Scott #1, The #1 was imperforate (no perforations to make separating stamps easier) and colored dull carmine. My stamp is vermilion (color) measure at 6½ perforations per 2 centimeters. Most of my stamps are effectively worthless even though the minimum catalogue value always shows 25 cents.
In this country most public libraries have a set of Scott Catalogues available to the public. I know nothing about what is available in New Zealand. Checking the values for yourself with the catalogues can be a time-consuming job requiring a lot of patience. I have always enjoyed it, but then I have almost always been a collector.