I don't think you need the heater, they're good about keeping themselves warm as long as you have lots of fleece blankies for them. And any kind of heater that goes in the cage is dangerous, such as a heat rock, they could electrocute themselves, over heat, blister, etc.
Also I think it would have been easier to get a bonded pair, you'll have to read everything you can about intros and pouch swapping, and making sure their cages are far enough apart. And something I learned on this site is that it's very important to wash your hands if you touch one and want to touch the other while they're separated, they will bite of they smell another suggie they don't know!
Bonding can take a long time, so just be patient and give them their space. Wait for them to come to you don't try to pick them up right away (most of them don't like being picked up anyway). Okusandman is right - don't get discouraged if they dont like you at first, it just might take a while.
Also changes like car rides home and new people can be stressful on them so if you can, I would make sure you're the only person theyre introduced to for a while. And to help settle them in, calm them down, and even help bond, you can just let them hear your voice. Repeat something soothing to them in a quiet voice like "it's okay" or "mammas here" it works on mine like a lullaby :)
A nice way to help bond with them is anytime youre just sitting around, get a bonding pouch and hold them close to you. You can just talk to them or sing, but let them hear your voice and get used to it and your breathing. Also to get them used to your smell you can put a T-shirt you've just worn over their cage at night.
Oh! And if you ever have an escapee don't chase them and never grab the tail even if you think you have to! Anytime you have them out of the cage have a fleece blanket large enough to cover them or treats nearby that you can grab either cover them and slowly scoop up or to lead them back to the cage or on you with the treats. If they escape from the cage while your not around turn all the lights off in the house and make the house silent. Have their favorite food ready so that you can put it in the room you hear them in and they should come right to it.
I hope all goes well with your new babies & good luck being a new mommy!