Oh yes, this is a great idea for a role play, @Maxine707! May I suggest another variant to also consider? (I'll write from a boy's perspective, but sexes could of course be interchangeable.)
Both parents work, so your neighbor, who is only a year or two older (maybe home from university for the summer?), offers to take you to the doctor for a sick visit. Protocol at the pediatrician’s calls for an adult to be present, so the neighbor stays in the exam room as you undress to your briefs and hop up on the exam table. Maybe she even helps by folding your clothes before sitting down in the “parents” chair.
As the nurse takes your pulse and blood pressure, you can feel some pressure in your briefs and try hard to think of anything else to stem the rush of blood. The nurse then says Mom indicated by phone that your temperature had been taken rectally at home. This makes you blush from embarrassment, and your neighbor definitely perks up imagining that. The nurse needs to get a comparable reading so instructs you to remove your briefs and lie down (naked) on your tummy.
As she inserts the thermometer, your penis presses hard against the crinkly paper. You’re petrified to even move lest your agitation become visible. You see your neighbor all flushed as she observes the procedure. The nurse holds the thermometer in place as it registers, chatting casually with your neighbor about how it's sometimes hard to get an accurate oral reading on boys.
Finally, the thermometer is removed, and you have to roll back over for an abdominal auscultation…