Every rider has their own style on what they like to bring on the ride but for those looking for some ideas, here are a few suggestions. The ride itself is about 2+/- hours of biking for a person of average fitness (including many families with kids).
Every rider must have a good bike helmet and a bike. Orcas is hilly and would be difficult to ride without gears (though it has been done). Beyond that you do not need any super special equiptment. Mountain bikes, road bikes, cross over bikes will work fine. The main route is all on the shoulder of the road. There is an alternative route, for the adventurous, that is off the beaten path and includes some dirt roads.
Like hiking, it is wise to dress in layers when biking. That way you can stay warm when you need to and cool off when you want. Orcas is in a bit of a rain shadow and often the air can be cool on that weekend (about 65) and partly sunny. This is actually ideal biking weather. Virtually every trip, our family typically wears shorts and a t-shirt with a thin nylon pants and a medium weight jacket/wind breaker. If you are easily cold, you might include a sweatshirt, warmer coat or warmer pants. If it is expected to be really wet, you may consider rain gear but that is rarely the case. If it is going to be sunny and especially sunny and over 70, bring less clothes and more water. Other things you may consider bringing according to personal preference: sun glasses, sunscreen, chapstick, gloves, hat. You may consider a backpack or some place to put all your clothes and stuff when not in use.
Lunch, Snacks and Water:
You will probably leave rather early on Saturday morning to get to Anacortes on time. Around 9 or 10, once on the Ferry, you will probably be hungry. Muffins and juice are served to the group, but if you want other snacks then or later, you can either bring them or buy them on the ferry. You will also want either bring a lunch or plan to buy one at the Bite of Orcas in East Sound or at the grocery store also at East Sound. You will also need to bring your own water or drink. Remember if it going to be hot and sunny bring lots of water. The grocery store is also a great restocking spot for drink, if you need it.