McVick, that secure sleeper is exactly what I was thinking of. I saw those at Toys'r'us. I think if we put that between us in the queen-size sleeping bag, with her in an additional fleece sleeper thing, that would work. The change pad is another really good idea. Thanks. These things should also help with the wriggling.
Not to suggest this is the be-all-end-all for everybody. Just for our situation with the somewhat cramped Maggiolina. I really like those Pea Pods for warm weather in a big tent.
The little swaddling sleeping bag thing wouldn't work. She likes her arms above her head. Doesn't like to be swaddled anymore.
Now it still leaves the question about the 4 year old boy. Last year, he slept in his own sleeping bag on his own mattress in the family tent in the height of summer. No problem with warmth. When we camped in September, it was quite cool. Probably 40F at night. In that case, we all slept in the Magg, with him simply between us in the queen-bag. The wriggling was a problem though.
So now with the baby between us... where does Phil go? I have thought he could sleep between us, rotated 180° at the foot of the bed, in his own little bag on top of our bag. Or is he ready for his own space? I'm sure he'd be fine down there alone, meaning, he won't be afraid. It's more ME that's afraid. He'd be directly below us, behind a plywood wall, with a hatch that locks with a dead bolt. I think he'd be safe from anything at night. My only fear would be him getting up and wandering off or something. Or, what if an electrical fire started in that compartment? I guess I could put a battery operated smoke detector. That would help a lot! And I've seen battery operated, wireless door chimes. We could hear if he opened the door for some reason.
My plan with the trailer was, when he's 6, Elise will be 3, the 2 of them can stay down there, no worries. But is 4 too early? I think a smoke detector would give me huge peace of mind. As would a door chime.