My wife's parents found some savings bonds that her grandfather left to my wife (thank you!). They fully matured in 2017 (i.e. purchased in 1987), but were just found. We want to cash them in, but the interest will be taxable and could be a decent amount. Any advice before we pull the trigger on cashing in? We've never dealt with savings bonds before. 

We have thought about paying tithing with them as a donation in kind or contributing them to a donor advised fund to avoid taxes on the interest. Not sure if there are other tricks or strategies in this space. 

TIA