I'm not from St Louis but, I'd like to help if I can. Myself, DH, and DS (6 yrs old, 5 at the time) drove from a little town north of KC Missouri last June. I've listed the break down of our trip below. A few tips I can offer to you would be:
1) Book a room if you think your going to need a place to stay on the way down and the return trip, we looked for a place to stay on the way down for over an hour...on the way home we looked for a place to stay all the way between Murfreesboro, TN and just east of St Louis and never did find a place to stay. We ended up driving home straight through but, I would not ever want to do that again, we left Orlando Fri 130pm and got home Sat 9am...we lost a lot of time looking for a room. My husband did not want to book one because he wanted to see how far he could make it, not a good idea!
2) If you have children, get a DVD Player or VCR....this was a life saver.
3) take snacks and stuff with you. We packed sandwich fixings, chips, fruit, drinks, and salads so we could eat in the car. We actually found a really nice place to have a picnic which was awesome.
Left Lawson, MO SAT 0522 AM
Stopped just east of St Louis SAT 0906 AM
Gased/Break at ALT 41 in KY SAT 1236 PM
(stopped for 35 minutes (300-335PM) for a picnic at Rest Area in TN (beautiful view))
Gased/Break at Exit 296 SAT 0447 PM
Gased/Break Exit 18 Valdosta, GA SAT 0935 PM
((looked for a room/place to stay), finally found one in Lake City, FL (Super 8, not recommended))
Left Exit 423 Lake City, FL SUN 1009 AM
Arrived at WDW-Boardwalk Villas SUN 1230 PM
TOTAL HOURS 17.50
Hope this helps!