You may be able to catch the dogwoods in Smoky Mountain National Park. Or the cherry trees in Washington. And of course there's Nashville with the Opryland Hotel. A bit expensive, but you can stay nearby and just visit the hotel. There are other places to see in Nashville like Music Row and the Rhyman Auditorium (the original Grand Old Opry) For gems, try digging for diamonds In Crater of Diamonds Park in Arkansas, or near Phillipsburg, Montana, there are Sapphire mines, my favorite
I second the list that included Yellowstone. We spent 8 summers there volunteering in a Ranger Station. Be sure to allow time to see it though. You might be there too early. The snowplows don't always get the roads open till late April. Great Falls, MT has a good museum about Lewis and Clark expedition. So much to see, so little time! Quilt Shops are all over the place, so don't spend all your money in one place!