You'll almost certainly have time to travel! The odds of a sim dying of old age before hitting 90 days are almost unspeakably low, and most of the time you'll get between 3 and 5 weeks after the Elder birthday. You've got 2 weeks until the teen ages up to YA, the game clock doesn't run while you travel, and you don't have to wait to harvest the plants, I think it counts when you plant them! So. Don't panic. Take a deep breath. If you get the opportunities it'll be cool and you won't have to travel. If you don't, you've got Plan B.