I would be somewhat concerned about the RIRs picking on the Silkies. They known to be a bad breed when kept in multiple numbers, and in fact it's recommended that in mixed breed flocks only 1-2 of them are kept to prevent them from forming a "gang" and feather picking the other breeds.
If you were to get Silkies, you would need to get at least two. A single Silkie wouldn't even stand a chance when put in with 2 adult RIRs. I'd still be wary with 2 (or even more) Silkies, but not quite so worried.
Broody hens can be a pain in the ***. They do not go broody when you want to - they go broody when they feel like it. This can mean never going broody, it can mean going broody the month before or after you have time to deal with the matter, or it can mean brooding for 3 months straight even if you don't want any more chicks. They can also sabotage themselves - moving to a different nest half way through incubation and killing the eggs, or giving up 3 days before hatch, or kicking the eggs out of under themselves.
Incubators can also be a pain in the ***. Unautomated ones require turning, even automated ones require the addition of water, and a drafty room can screw up the temperature pretty easily. However, they are overall, much less of a pain in the *** than broody hens. What you are paying for is the knowledge that unlike a broody hen, the incubator does not have legs, and so cannot get up and abandon the eggs at any moment. You are also paying to know that as long as it's kept in the right conditions (draft free room, no direct sunlight, etc.) you have the IDEAL incubation conditions and are giving the eggs the absolute best chance at life.
My personal recommendation is an incubator. While I do enjoy broodies when they manage to bring a clutch of eggs to full incubation (which I would estimate only around 40% of my broodies are capable of doing or have done), my little
Brinsea 'bator gives me consistent hatch rates, allows me to easily view the entire process, and can't starve it's offspring to death due to it's own stupidity (which my Silkie hens have, in fact, done in the past). If you do choose an incubator, I recommend the
Brinsea Mini, or really, any
Brinsea model - they are the best incubators available (if a tad pricey). The Eco is around $100, and does not come with an autoturner. The Advance is around $180, and comes completely automated - all you need to do is add water every ~3 days. I can't speak for the Eco, but my Advance is a little wonder - it gives me consistent 80-100% hatch rates of chickens, turkeys, guinea fowl, etc. I wouldn't trade it for 100 broody hens, even if they were the best brooders in the world.