Edited Comment:
Hey S.: Thanks for the email and clarifying the age of your kids... (Your son is the baby). So I've been thinking over your question, and I was reminded of a conversation I had with another mother friend of mine about how our girls (both young 2 yr. olds, as well as the other girls in their daycare class), seem so much more mature than the boys their same age... More verbal, more control of their emotional outbursts, more balanced with motor skills, more self-aware of the difference between "big girls" versus younger kids and "babies". Child psychologists always say that the brains of girls and boys are different... Maybe there is some other nervous system wiring or brain development happening in boys at this age that just takes longer; perhaps boys just stay in what we see as a baby stage for 6 months longer than girls..? Maybe this extra maturity time allows boy brains to develop that particular affinity for math and science... or at least the fascination with destroying & exploding things!!!
So if you are use to how and when your daughter and step-daughter reached milestones, it might be frustrating to have the same expectations for your son. I still think however, that his tantrums (restaurant behavior) center around the realization that it gets him extra attention from mommy and daddy, especially if he has to share you with 2 older kids. I'm curious... Does his fits or clingy-tantrums come on when the attention gets diverted away from him and to one of your other kids?
I would start to ween him off the bottle. I had a dickens of a time with the bottle to sippycup transition with my DD, and found that using straws worked wonders in getting her interested--especially is she could pick the color to use and stick it in the sippy cup herself (bought sippycup sport bottles and replaced the straw insert that came with it with the regular plastic straws).
Perhaps reading some potty books to him will help prepare him for when he is closer to 3.
Good luck!
Initial post:
Do you have a younger child too? Sounds it could be sibling/new baby jealousy, but you only mentioned 2 of your 3 children. In any event, sounds like he's figured out that this behavior gets him more of your attention.