Is it moraly o.k. to let a 2 1/2 year old boy play constantly with his erected penis?

Yes, it's OK.  It's not sexual to him it just feels good.

Lots of toddlers masturbate.  Don't make a big deal of this.

I AM A MOM OF 4 BOYS,AND ONE GIRL,AGES 4 TO 11.......i never force my kids to wear cloths in the home,and on our farm.......erections are natural....while playing,breastfeeding ,and there is nothing wrong WITH HAVING GOOD feelings........only problems is a body image, that is created by repressive Victorian type thinking,which is very harmful to the child's mental well-being.it's all how you comprehend and understand it.

My 26 yr old bro has severe autism and he is very much like a toddler and he is ALWAYS naked so he is playing with himself contently but to him it feels good and the talk went right over his head so we just let him do it. Yesterday in the tv room he was really getting into it.