Age Appropriate?

We have a 7 year old son who does not pronounce his R's or L's and has difficulty with other sounds, such as the word "good" sounds like "guud". He frequently acts like a two year old in his actions and speech (high frequency, baby terms, descriptive terms, etc.) and when excited, his face exaggerates by opening the eyes wide, smiling a very big (unnaturally big) smile and clapping uncontrollably. This behavior is observed about 30% of the time. He also continues to wet the bed three to four times a week. He seems to play normally, can entertain himself for hours with toys (action figures, building blocks, etc) and does not appear to have any motor skills problems other than the speech.  As parents we are concerned that he may have some kind of developmental issues, maybe even mild Autism, but we just don't know - are we being over concerned? Our 9 year old had none of these issues and our 4 year old more often than not seems to be more mature then the 7 year old and does not exhibit any of these symptoms either. Any insight would be very appreciated.  Thank you.