Use the battery drain calculator in steam engine. The ohm's law calculator is pretty much the same, but the battery one is more intuitive and has other features that help, such as showing the headroom x build leaves for y battery, lifespan, and so on.
If those Sony's are VTC4's, then a parallel configuration leaves you with plenty of headroom for a build like that.
Like martnargh said, the amp load is split between the batteries when they're wired in parallel. This essentially doubles your amp limit, while voltage stays the same.
This means that if you have a coil that pulls a total of 20A, then each cell will (ideally) contribute 10A. I say ideally because it doesn't always work out that way... ...slight variations in the internal resistance of the batteries, a resistive bias on one side of the circuit path, inconsistencies in connection points... ...point is, it's likely not an even split. One battery may give more current than the other, which means you have a little less than double the headroom.
In a perfect world, two 30A batteries wired in parallel will give you a net CDR of 60A. However, it's good practice to assume that the world isn't perfect and stay 20%-25% under. It's a good general rule to stick to at least until you're familiar enough with batteries to have a better idea of what specific ones can and cannot take and what the signs of over-stressing them are. Some batteries can take more abuse than others, but knowing where the line really is takes some research and know-how. Best to stick to the actual rated CDR.
Just make sure the rating is real. If the battery is branded anything other than Sony, Samsung, Panasonic, or LG, then it is a re-wrap of one of those and the specs on the wrap are likely exaggerated. You will need to search around to see what the battery under the wrap is and what it's actually rated for. As long as your Sony's are real, then you can trust the CDR... ...just something to know for the future.
Getting back to the 20%-25% rule, if you have a single 30A cell, stay close to 23A and not much more. Single 20A cell, ~15A. Two 30A cells in parallel, ~46A...
...abiding by this rule and assuming 20A batteries, you can go as low as .14 and be right at 30A. I personally wouldn't advise it, as it's generally an unnecessary amount of power unless you have very specific goals. It's always best not to get into high-current if you don't have to. I'm just saying that as long as you have a pair of batteries that can take at least 20A, then you won't have much to worry about until you start approaching that resistance. And even that is playing it fairly safe.
But again, make sure your batteries are a minimum of 20A. Cannot stress this enough!
