Can I just start by saying....Thanks for even *caring* about etiquette at
Disneyland???!! So many people don't, and it seems like it gets worse every year - so know that there are many of us who REALLY appreciate it when someone actually considers how their actions in the parks affect everyone around them.
While it wouldn't really bother me personally if it was just a Dad & kid getting in line at the last minute (as opposed to, say, half a dozen family members meeting up with the ONE who stood in line...), you might want to plan ahead which lines you are considering doing this for because it would be more difficult with some than others. For instance, the walkways up to POTC are kind of narrow until you get inside, as are others. And I would think Jungle Cruise would be really hard to use that strategy on, as well. Additionally, pretty much ALL of the FL rides have very narrow, zig-zagging queues that would make "catching up later" kind of a challenge, IMHO.
Other etiquette tips:
If your little one becomes really distressed in a show (like Aladdin) and gets really loud, it would be great if Mom or Dad could stand outside with him. We've only gotten to go into Aladdin once, and 3 or 4 different families were letting their kids howl through the entire thing and never made any attempt to take them out. I have 4 children myself and have spent my fair share of time walking theater lobbies so that my kid didn't ruin the show for everyone else - would love it if others would have the same kind of consideration!
My all-time pet peeve in the parks is parents who let their kids bounce around so much that they are repeatedly bumping into and/or stepping on people in line next to them. Again - I have 4 myself so I know kids can get wiggly....but still - it's not OK to let them repeatedly ram into other people.
Last time we were there (in January) a woman next to us let her little girl, about 3 years old, LITERALLY *lick* the entire length of railing along the whole queue of Alice in Wonderland. I hope I don't even need to explain why that would fall in the category of poor etiquette, LOL!!!
Hope your family has a fantastic time!!