this website has some good suggestions for ft worth, at the bottom of the page

http://www.metromaples.com/catalog2010.htm

Most Sun Tolerant - Upright: Acer palmatum, Sango Kaku, Seiryu, Omureyama, Osakasuki
Most Sun Tolerant - Dissectums: Tamukeyama
Most Sun Tolerant - Dwarfs: Shishigashira, Mikawa yatsubusa, Coonora Pygmy

You will get differing recommendations from different sources, but the upright, larger leaf red forms are noted as having very good sun tolerance - 'Bloodgood', 'Emperor I', 'Fire Glow', 'Bonfire', etc. Not all will retain the dark red coloring uniformly in full sun, but if given decent, well-draining soil and sufficient irrigation, you should not experience scorching.

If you search through the archived threads on this forum, you will see this issue discussed frequently. No doubt there will be additional choices others have had exerience with in full sun and warm temps.

I don't get quite as much heat as you, but it can get very hot in the summer here - long stretches in the 90's.
I have a Hogyoku, Osakazuki, and Boskoop Glory in full sun and they're doing fine. The Boskoop Glory greens up quite a bit in summer, but has the most glorious flaming red-orange fall color!
My Bloodgood's leaves can look a bit shabby, though, after a full summer of hot sun.

Are your trees mature enough to keep them but limb them up by cutting the lowest limbs off? Then plant Japanese maples in their shade possibly? Just a thought, it works well for me.

swmogardens' suggestion sounds like a really great idea - I'm not sure ANY JM is going to deal with weeks of 100+ temps without drying up.