new All Grain brewer...technique question

my first all grain brew this weekend. it calls for a protein rest at 122f for 15 minutes. so here's my question:

calculator says heat my 14.6 quarts of water to 136F, then add my grains for a protein rest temp of 122F for 15 minutes. can i then just turn the heat on and stir as i bring the mash temp to 152F, where I leave it for 60 minutes in my igloo mash tun?

seems to me that makes more sense than heating part of the water to 122F for the rest, then adding remaining water at higher temperature to try and land at 152F for the mash.

Bavarian Dunkle weizen
Style: Weizen/Weissbier
Type: All Grain Calories: 164
Rating: 3.5 Boil Size: 6.35 Gal
IBU's: 10.17 Batch Size: 5.50 Gal
Color: 14.6 SRM Boil Time: 60 minutes
Preboil OG: 1.047
Estimated Actual
Brew Date: - 12/17/2012
OG: 1.050 1.050
FG: 1.013 1.013
ABV: 4.85 % 4.85 %
Efficiency: 70 % 71 %
Serve Date: 01/21/2013 / /

Fermentation Steps
Name Days / Temp Estimated Actual
Primary 21 days @ 69.0°F 12/17/2012 12/17/2012
Bottle/Keg 14 days @ 38.0°F 01/07/2013 -

Grains & Adjuncts
Amount Percentage Name Tim Gravity
5.00 lbs 43.29 % Rahr White Wheat 60 mins 1.038
3.30 lbs 28.57 % Rahr 2-Row 60 mins 1.035
8.00 ozs 4.33 % Briess Carapils 60 mins 1.034
1.75 lbs 15.15 % Caramunich III 60 mins 1.037
1.00 lbs 8.66 % Dark Wheat Malt 60 mins 1.038

Hops
Amount IBU's Name Time AA %
0.60 ozs 8.72 Tettnang 60 mins 4.50
0.50 ozs 1.45 Tettnang 5 mins 4.50

Yeasts
Amount Name Laboratory / ID
1.0 pkg Hefeweizen Ale White Labs 0300

Additions
(none)

Mash Profile
Protein Rest 15 min @ 122.0°F
(Add 14.40 qt water @ 134.8°F)

Medium Body Infusion In 60 min @ 152.0°F
(Heat to 152.0°F over 10 mins)

Sparge
Batch Sparge 23.00 qt of 170.0°F water -collect wort over 30 mins

Although I have no experience in this type of mashing protocol, I've read that the risk is scorching of the mash at the bottom of the kettle, and also potentially denaturing needed enzymes in part of the mash that may get too hot...

Pretty adventurous jump into all grain brewing...good luck!

That's fine. The one thing you may want to consider is that your mash tun will be cold, and will drop the temp of your mash. I would either pre heat the tun, or overshoot the temp before you transfer.

for a first AG, i'd skip the decoction and go for a single infusion. you have a lot of other things to worry about. walk before running

Beer Smith handles the water temps pretty well. Make sure you check the box to adjust temperatures for equipment. Input your MLT and grain temp and you are good to go.