Recreational & Family - Double up trail a bikes? Can you do that?

My family has now grown (good!) so that I am not sure how to fit everyone riding at once (bad!). My daughter is nearly 5, and my sons are 3 years and 6 months.

Our current set up is the bike train (I posted a pic a while ago) with my daughter on the Adams trail a bike and my son in the trailer behind her.

The problem is that I want to take the new baby and am not sure how to take all three.

If I had more money, I would simply get an Xtracycle conversion.

There is a good used Adams trail a bike for sale locally for cheap.

My question: Is it possible to have two trail a bikes connected to one another? If so, then the bike train would get pretty long. My concern is not the length, but the height of the seat post needed for attachment. The height of a trail a bike seat post is quite a bit lower than an adult bike. would the second trail a bike be sloped forward?

Any thoughts?

Here is a photo of a normal trail a bike (http://http://www.google.com/imgres?q=adams+trail+a+bike&um=1&hl=en&qscrl=1&nord=1&rlz=1T4DKUS_enUS242US242&biw=1280&bih=577&tbm=isch&tbnid=8bKGuli0RKZqGM:&imgrefurl=http://cargocycling.org/family-cycling&docid=Z6eRJF7XphcPQM&imgurl=http://www.cargocycling.org/images/2007/03/19/adams_bike_2.jpg&w=365&h=193&ei=fhG4T_GwMYj49QTj39HZCg&zoom=1&iact=hc&vpx=709&vpy=187&dur=3894&hovh=154&hovw=292&tx=94&ty=82&sig=112204059919963711656&page=3&tbnh=87&tbnw=165&start=36&ndsp=25&ved=1t:429,r:10,s:36,i:180), if that helps.

I guess it isn't a huge deal if it doesn't work. I could beg my wife to come cycling and attach the other trail a bike to her bike.

Still though, it would be cool if it worked.

How would you take all three with two trail-a-bikes? Would you put the baby in a front-mounted seat? Is there a reason a double trailer with the two younger ones wouldn't work behind the trail-a-bike? If you want your 3-year old to start helping with the pedaling, you might have to bite the bullet and get the Adams tandem trail-a-bike and put the baby in the back in a trailer or in a front-mounted seat. Alternatively, you could look for a cheap tandem you could retrofit with a child stoker kit and put the trail-a-bike on the back of that.

+1 to mel2012 post - and to answer you original question - you won't be able to keep both TABs upright. I have a single TAB and a double TAB and just pulling two kids on the the double TAB is at the edge of my comfort zone of keeping them up.
Convincing your wife seems like the best idea :D
Another thing would be to use a good baby carrier on your back, like Ergo (http://store.ergobaby.com/), but maybe when your baby is older and can keep the head upright (around 1yr?). My kids spent some time on my back while cycling and they loved it.

I've been thinking about kid-carrying options too since my son's at the weight limit of our Bell carrier, plus his first sibling is due in a month. To me, the "FollowMe" tandem coupler looks really nice, though pricey at $400 and apparently hard to get in the US. Since it attaches to the adult bike's rear hub, a rear-mount kid seat could be used at the same time.

That tadem trail-a-bike does look like an interesting option, though I'm slow to understand these systems that attach up top. I'm also considering the heavy-duty "Bobike Junior" kid seat ... for the tinier one, I guess I might consider a front-mount seat if I ever figure out how I'm supposed to avoid hitting myself on it!

I also really like the concept of a stokid tandem. The price of entry looks like it'd start around a grand, which is a little steep since I'm not used to spending much on bike stuff, but I guess I'll have to compare it to the cost of the gizmos (especially those not sold locally for $affordable) to hook everyone up to my existing bike!