I'm glad that you're taking your son to the doctor. His level of speech sounds similar to my grandson's at that age. His pediatrician suggested having a speech evaluation and told us about the Multnomah Co Educational Service District. By Federal law all school districts have to provide assistance to any child who has a condition which would cause him to have difficulty in school. I'm sure that you have the same service in Olympia.
They diagnosed my grandson with speech apraxia which in his case means that something doesn't happen when the message is sent from his brain to his mouth. The muscles that he uses to talk have to be trained. Leaving off part of the word is one of the signs. So are excessive drooling as a baby, stuffing their mouth with food instead of taking just one bite, keeping his tongue outside his mouth. There are several more which you can find on the Internet.
My grandson is now nearly 4. He's been in treatment for one year and is getting better with speech but he's still very difficult to understand and he still only uses 1-3 words at a time.
Here are a couple of Internet sites:
www.aafp.org/afp/990600ap/3121.html
www.//tayloredmktg.com/dyspraxia/da.shtml
It is extremely important to find out why he isn't talking and to get appropriate treatment now. Kids who are still having speech difficulties by the time they're in first grade continue to have both social and learning difficulties throughout their school career. Also there is one program available only until the child is 3. By happenstance my grandson got started before he was 3 and as a result a speech therapist came to their home.
Evaluation and treatment thru the Educational Service District is free. Private evaluations and treatment are expensive and not always paid for by insurance.
This process is scary at first. And we all want to think our child is just a late bloomer but frequently there is a physical condition for it.
My grandson is getting much better overall. In addition to speech he is learning how to follow instructions, how to do some activities, such as putting together a puzzle, that he wasn't interested in doing before, and how to get along with other kids.
For a child with muscle or cognition difficulties having the parent clearly say words does not help. He doesn't have the muscle strength to say them or the message isn't getting from his brain to his mouth. This is also true of asking him to repeat after you and/or correcting him. This just makes him more frustrated because he cannot do it.
A suggestion about your daughter's difficulty. Rice is a part of the brat diet used for diarrhea and so I would guess that might be the cause of difficult bowel movements. Be sure that she drinks plenty of water. You could try adding prunes to her diet. And you could thicken her food with dehydrated potatoes.