Usually the time of day dictates what is served for food. If it's at a meal time (I'd say anytime between 11 and 1) lunch would be served. Later than that, I'd assume it would be light apps only and cake/desserts.
From the PP's, the only thing I differ from I guess is the idea of what is "a full meal." You can get a "full meal" from a sufficient amount of heavy apps, fruit, cheese, etc. In fact, most baby showers I've been to have had "lighter" meals even when they are "meals." The typical fare is finger sandwiches, some veggies, cheeses, fruit, some other appetizer, and some dips/chips/etc. It definitely fills you up so it's a full meal, even if it's not, say, a big old lasagna or something.
If you feel your guests would expect more than cheese & fruit & cake, then go for it, but I think you're okay with what you are serving based on when it was held. (I'd definitely eat before a party that started at 2 because that's too late for lunch and I'd expect it would be over before dinner.) It's also fine to put it on the invite, "Light refreshments will be served" so people are all on the same page.