All I can say is look very carefully if choosing "tree planting" to offset emissions.
The first caveat is that the trees are planted, but may not necessarily live, and even if they do live for a while, it may take decades before they actually cause an "offset".
The second is that trees that are planted are sometimes harvested, causing the offset to be negative, given that fossil-fuels are almost certainly used in the harvesting and processing of the wood.
The third is that the trees are likely to be plantation trees -- ie, a monoculture with little to no wild-life value. Wild-life value is important, because trees aren't things, they're normally part of an ecosystem that sustains itself, adds to soil carbon, and so on.
Or you could find a way to buy and plant and care for your own trees, and use your own labour, which would be a thoroughly honest way to go. Having planted a lot of trees, there's nothing like looking at a tree you planted 10 years ago and is used by birds and insects and shade for animals.
Lastly, if you do have thousands of USD, possibly the best carbon offset is to either fund a activist group to get in people's faces about the larger problems, or to buy political influence to pass more environmental protection legislation.
