A lot depends on the rabbits. Some won't care about a litter change while others will protest at the slightest change.
A gradual change is probably best. Start with the equine fresh on the bottom with the yesterday's news on top. Instead of dumping the whole box each time, scoop out the soiled litter and mixing the 2 together. This can allow them to get used to the new litter more slowly. You will have to dump the litter eventually, but not every time you clean the box. Gradually decrease the amount of yesterday's news until it is all equine fresh. Hopefully with a gradual change they won't put up a fight.
The wood pellets can smell a bit woody at first, so open the bag and let it air out for a few days before you use it. Even if they don't have an issue with the texture, they might not like the smell.
If you have a grate in the litter box, it should hopefully go a bit easier. Since they are not sitting on the litter, they shouldn't notice the change.
I would go directly to a strait equine fresh for Silas. Since he is just starting litter training, it should go easier to just have 1 litter. If he has used yesterday's news before, he might resist the change. If that happens, then do a gradual change, but I would try just the equine fresh from the start .