First, it's much better to feed smaller meals through the day than two large meals. It helps keep the BG more level. Lantus is not the type of insulin that needs a big meal at shot time..it's much gentler than most other insulins. Many of us work and have the issue you are talking about, but there are ways to feed smaller amounts through the day when you aren't there....you can freeze the food into pucks or cubes and leave it out to thaw for fresh food later, you can add water to the food to keep it fresh longer (and the extra water is good for diabetic cats anyway!), or you can use a timed feeder to offer snacks at different times.
Home testing is the only way to be sure that it is safe to give the shots, and it's the very best way to assess the dose you are giving. The analogy of driving down the road with a paper bag over your head is a good one. Let me ask you this...if you were diagnosed with diabetes and prescribed insulin, would you give yourself insulin shots for 2 weeks without testing your blood? Wouldn't that be kinda dangerous?