I think 5 entries was the minimum for a class, but really it's at the race directors discretion. The problem you may run into is when there are 2 non-buggies in novice and 3 buggies, if you split up the class you end up with two very small classes. In that scenario, the race director would probably run them as a combo class and so it ends up being the same as if you never split them up n the first place.
The carpet track in Spring Hill has a separate novice buggy class, but the participation levels in regular novice and novice buggy are both quite high.
Best bet is to talk with the race director on race day during sign-ups to see if there are enough entries to split the class.