I don't think the Marek's is always necessary for a small backyard flock. You can call your local county extension office and ask if Marek's has been a problem in your area in recent years. They'll be able to give you the best advice about it based on your area.
If you are going to get the coccidiosis vaccine you need to be sure that non-medicated chick starter is readily available in your area, since you can't feed the medicated to chicks vaccinated against the coccidiosis - well you can, but it will nullify the vaccine which would be a waste of money. I've searched high and low and haven't found non-medicated chick starter anywhere within an hour's drive of where I live.
To me, feeding the medicated feed is the simplest way to deal with the coccidiosis threat.
BTW, Welcome to BYC!