ANSWER:
*sigh* the ER is for emergencies, this is NOT an emergency. A baby that is happy and playing is NOT a medical emergency (Unless they have swallowed poison in which case you don’t wait for them to get sick before you go).

The rash could be many things depending on how it looks. I am thinking fifth’s disease (not serious) -this rash is described as “lacey”. It could be heat rash. It is probably not contact dermatitis (poison ivy, allergy, etc) because of the rapid spread, same for eczema.

The fever is not concerning in a baby that age unless it is over 105F AND doesn’t respond to treatment. Otherwise it is certainly safe to wait until the next day or the day after to see a doctor.
http://www.drgreene.org/body.cfm?id=21&action=detail&ref=832
Older children with a fever (6 to 24 months old) who are acting well and have no other symptoms should be seen if the fever lasts 48 hours (or 72 hours if they do have minor cold or flu symptoms).

http://askdrsears.com/html/8/t082100.asp
WHEN TO PAGE YOUR DOCTOR

* Remember, fevers are your body’s natural response to infection, and not necessarily a sign that something serious is taking place.
* Low-grade fevers are generally not serious, are easily treated, and can wait until the morning to be evaluated by your doctor.
* Fevers of 101 to 103 (38.4 to 39.5 Celcius) are also generally not serious and can wait until morning to be evaluated, except as indicated below.
* High fevers of 104 (40 Celcius) or higher that quickly come down to 100 or 101 (37.8 to 38.3 Celcius) with the treatment measures below are also generally not serious and can wait until morning, except as indicated below.

So for now, don t rush to page your doctor. Read through this section, and call your doctor during office hours, or page your doctor according to the following guidelines

Picture of contact rash: http://askdrsears.com/html/8/t082901.asp
Picture of HAND, FOOT AND MOUTH DISEASE http://askdrsears.com/html/8/t082902.asp

Skin Rashes and Other Changes (flow chart)

http://familydoctor.org/online/famdocen/home/tools/symptom/545.html

http://askdrsears.com/html/8/t082900.asp
RASHES ARE RARELY URGENT, AND ALMOST NEVER REQUIRE AN URGENT PAGE TO YOUR DOCTOR.

In fact, there is basically only one rash that requires immediate medical evaluation this is a rash called petechiae or purpura, which involves ruptured blood vessels under the skin. We will discuss later how to recognize this rash. Virtually all other rashes can wait until you can call your doctor’s office to schedule an appointment. Diaper Rashes are discussed in a separate section.