The enchanments would be a great day trip and is less than 20 miles. I think it's ~ 18 miles through.
If you were moving fast, you could hike Little Annapurna, and scramble McClellan. If you were moving really fast, you could scramble Enchantment as well.
It's a rough loop that puts you about 10 miles away from your car. Leave a bike at the Bridge creek entrance. Start hiking at Snow Creek. Ride the bike mostly downhill to get the car and your partner.
I know, it's not the North Cascades....