I was on an airplane 2 weeks ago and my checked bag was opened by the TSA.
Because of the layout of the Kansas City airport, I was able to watch the search.
She just lightly lifted my clothes (neatly folded and packed because this was the
beginning of my trip), then ran a paper towel-like rag around the edges of the bag. I think it was to check for explosives residue.
If the tent is in the drawstring bag, it shouldn't pop open regardless of what kind of search happens.
There is information at this website about luggage restrictions:
http://www.tsa.gov
It is good to check, because the restrictions change frequently.
You should also check your airline's web site for weight restrictions on each bag. They vary quite a lot (some are 70 pounds; some are 50). The surcharges for overweight luggage are substantial--like $40 per bag.
It may seem like a lot of work, but you don't want any surprises at the airport.
Oh yeah--wear slip on shoes, and don't be surprised if they check the baby. People HAVE been know to conceal explosives in a baby's diaper.