Hi!
I've never actually dealt with baby rabbits--how old do you think you will get? The youngest I've dealt with is about a year or two old, but I know a bit about taking care of younger buns.
I also don't know how he will do with the guinea pigs. If they start fighting, you should probably keep them separate.
Like TheTwoRoos said before me, you're going to want to have him fixed.
Do you have feeding and housing planned out, yet? Not only for him as a baby, but as an adult?
When he's a year or two old or younger you can give him alfalfa, but stay away from it when he gets older. I suggest giving unlimited timothy hay and a timothy hay based pellet, but that's just me. You can give them other grasses as well, and a timothy hay based pellet isn't needed. But that's what I give my buns.
I view pellets as more of a supplement rather than an actual food source. I give them one scoop every morning once a day. (Especially since I have a 10 year old rabbit who's digestive system can't handle too many pellets anymore. But that's not your problem)
Also on the note of pellets: don't buy the grain-based pellets that also have the weird dyed stuff in them. Grain is bad for bunnies.
You'll also want to give him safe, cheweable toys. I'd personally stay away from all the dyed and 'commercial' stuff commonly sold in the pet stores, and try to find the more natural things like wood or undyed items like grass mats.
I notice a lot of people will give their buns greens daily. I don't. I give them more as a treat, but again, that's mostly because my older bun can't really have a lot anymore. Even when he was younger, it doesn't make a crucial difference if you do or don't give daily greens.
Will you be keeping your bun inside or outside? With inside you'll not only have to litter train him, but change out his litter box every few days. Like TheTwoRoos said before, again, it does get stinky! (I now have my buns outside in a hutch--we both love the change a lot better, lol)
If you keep him outside, you'll have to make sure you keep him cool during the summer and warm during the winter.
Also, make sure your bun gets exercise. Whether it's letting him run around your house or buying a pen (I suggest a dog pen--it works great) to set up in your yard, they need a chance to stretch their legs.
Also don't forget grooming and nail trimming. I have a rubber cat brush that works great on my buns, so you could look into something similar. I also have either a dog or cat nail trimmer? That works fine for me. You usually need a partner for clipping nails, unless your bun is good about it and you can handle it yourself.
Well, that was very long, but those are the basics. Hope I didn't repeat anything you already know. If you have any questions, I'd be happy to answer!
