We're a family of five, and $100 extra per night is absolutely worth it for us. Here's why:
1) Breakfast. If we're at WDW for a full week, we'll do a couple character meals. But generally we're happy with a quick breakfast and there isn't anything more convenient than CL for that. So while I factor in the amount we'd spend on breakfast for five (even at a CS,) the convenience factor is huge. Before we started staying CL, we'd do breakfasts in the room quite a lot - not as convenient, not as healthy (hard to keep that fruit fresh over several days), can't sit down all together, no protein and it's just a different feeling trying to eat in the room from packages.
2) Snacks. We don't buy as much in the parks - either in the afternoon or after dinner - because we have snacks and desserts available in the lounge. Not sure how that works out dollar-for-dollar, but it's very convenient.
3) Evening appetizers. I usually won't book CL if we're not planning to take advantage of this time. When we do, it's great. First, it's a nice break in the late afternoon before dinner (we usually have 7pm ADRs.) It's a reason for everyone to slow down and have some down time. At home, our kids have hot snacks after school a few hours before dinner, so it fits their eating style. (We generally eat smaller snacks and meals, rather than large meals.) When we get to our dinner ADR, nobody is super hungry, which is good. And we order much less at dinner as a result. I usually have a couple glasses of wine and my husband gets a beer, so given Disney prices, that's about $25 right there! We did cold packaged snacks in the room several times - before CL - they just aren't a draw for my husband or the boys, not as healthy and there is a ton of waste. (Just stayed non-CL last month with our youngest son - it was just two of us and we left an entire grocery bag of snacks behind.)
Good luck with your decision!