What a kind and wonderful heart your Uncle was to have thought of you in his will. Five grand isn't a huge sum of money like, say, $50K, so choose carefully. I think he would have been tickled pink if you did something special for you, his chosen beneficiary.
Can you and hubby take a 3 day weekend to a lovely resort in the mountains and have a special time, and lift a glass to your Uncle?
Maybe get something special for yourself, that watch you have always had an eye on, and think of your dear Uncle every time you put it on.
Go to the dollar store and fill up a few dozen care bags for the homeless, comb, toothbrush/paste, water, crackers, canned meat, socks, paper/pen, deodorant, soap, cloth, gum, flashlight. Pass them out as you see the need and thank your Uncle for the legacy.
Seek out an organization in a developing nation that is rescuing under age girls (some younger than 8) out of sex trafficking, and teaching them a craft, and buy all the bracelets the girls are making and take them to a local nursing home and pass them out and love on the elderly.
All of this is so much more fun than applying it towards your mortgage!
Bless your uncle!