I love my SMALL Camelbak (CB).
I have 2 CB's. One is around 1 liter and is perfect. I don't notice it on my back and when filled with ice and water, I have cold water for hours (even in 100F degree weather).
My other CB, I purchased for the MS150 so I would be able to carry more water and stuff in pockets. It's approximately 2 liters. UGH! After I got the pockets filled up and the bladder full of water, it was TOO HEAVY. I even had to empty most of the water out.
Now, the MS150 is heavily supported. You typically have rest stops every 10-15 miles. You can do it on water bottles.
Oh, and I see you live in Dallas. After you get your road bikes, might I suggest you look into the Greater Dallas Bicyclists? We have a great group and many ride options for all levels. And, it's nice to be able to ride on the roads and not be scared (when you have a group of 30 riders- cars contend with us, we don't don't contend with them).
On rides less than 2 hrs I think one bottle of Gatorade (or your drink of choice) and one bottle of water is enough. I freeze them the night before and they'll stay cool up to about an hour.
It's all about the POLAR WATER BOTTLES! I freeze mine and it works great. My frozen Gatoraid/water stayed frozen/cold from 8:00 AM to Noon this past Sunday (when it was 90+ degrees).
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"