Grammar for counting in Chinese (for non-native speakers of Chinese)
Regarding arabic numerals: I think modern usage sees arabic numbers to be generally acceptable. However the context of the material, or even the region, may influence whether they're commonly used or not. For example, in metropolitan areas you might commonly see phone numbers or prices expressed in digits, whereas in more traditional material you probably wouldn't. You may or may not be able to get away with this in your project.

Regarding 两 vs 二: 两 is generally used as "two" for specifying a number of objects, whereas 二 is used as the digit, such as in a phone number. See this question for more on this distinction.

Regarding the classifier: As far as I'm aware, there's no such rule as 1-6 uses this classifier, 7-9 uses this, etc. The classifier is determined by the noun. In your example, the classifier for cats (猫） is 只. For house (房子) you can use 栋.

The classifier for people is (usually) 个. Perhaps more importantly, 个 can be used as the catch-all classifier in casual language, or when an obscure noun has a classifier that you simply cannot remember. Again, whether you can use this "shortcut" will depend on the specifications of your project. In more formal situations, the correct classifier is preferred.

If you have a finite list of nouns in your project, you could spend some time looking up the relevant classifier for each noun.

http://www.mdbg.net/chindict/chindict.php specifies the classifier in the dictionary entries, denoted by the "CL:" text.

Hope that helps!