Magnuson had a teaser promo photo of a third gen Tacoma with the insinuation that it was being used to develop a supercharger. If you're worried about power the Tundra is the safe bet. Skip the TRD Pro packages and go with the TRD Off-Road if you want the electronic locking rear differential. Use the money you save to buy some nice King suspension and have a better setup than the Pro for less.
Magnuson is beta testing a supercharger for the Taco. They are about to release one for the 2015 4runner, I can't remember off hand if the motor is the same as the 3rd gen Tacos.
My take on your hunt for a new truck..
If you are coming from a full size pick up, you might not like the Taco as much as the Tundra. Sounds like you have a little one, also. Way more back seat room in the Tundra.
Also depending on where you might off road might also dictate, the size of vehicle. I have a '16 Taco, for my area of off roading it is a great size. I was also enamored by the TRD PRO version but it seemed like it was going to be amost 10K more. The TRD Tacomas do come with a modest 1", front skid plate, no sunroof (TMK) and leather seats.. Which as you probably know, leather is great with kids.. seems to clean up better than cloth.
I am not sure what the Tundra has in the TRD Pro version.
For me, I went with TRD OFF Road. Sunroof, rear locker, upgraded stereo. I lifted it with ToyTec Boss 2.5s, RIC Sliders/skid plate and a Demello front Bumper, FJC TRD wheels and BFG TA KO2s.
I was able to do all that for the price difference of a TRD OFf Road VS. a TRD Pro. Also My Taco can pull our Coleman Santa Fe pop-up trailer just fine. You feel it back there but it pulls great.
My guess is with a Tundra pulling, you might have to remind yourself you have something back there.. We have a 100 series Land Cruiser also and it actually pulls the camper with ease.