Although you may react differently than I do, but I donate regularly and have never had an issue. If you do decide to donate, make sure you drink more water than you normally would to replace the volume of lost fluid and eat a good meal before or after your donation. The 3 mile ride home shouldn't be a problem as long as you're feeling ok before you take off. You should also be fine for a longer ride this weekend, but you may not want to do a century or too hard an effort for at least a week.
Disclaimer - I'm not a physician nor do I play one on TV. I'm also not smart enough to stay at a Holiday Inn Express.