I think this is true of experienced programmers, but I see inexperienced programmers tripping over floating point misunderstandings quite often. In almost every case they shouldn't have been using floating point at all.
Some people feel strongly against this, but for dynamically typed language I enjoy its simplicity (for static languages, type systems are meant to enforce constraints on types, so multiple number types can be useful). It has done well in [at least] javascript and lua, and while the former is anything but an example in how to design a programming language, IMHO, the latter may be.
So no, it wouldn't be a bad idea to make all numbers 64-bit floats. It sounds like you might likely be compiling to javascript, in which case using 64-bit floats will mean you have one less problem to deal with while implementing it.