I started as a parent helper, mainly supporting 'readers'. One of my first Yr1 girls turned up again seventeen years later, in another school, on her final year of Teacher Training; roles were reversed, as SHE needed to direct ME in the classroom!
I became a TA for twelve years, plus ten or so voluntary years.
Your IT (ICT in school) experience would be valuable in classes I would have thought, as that is one area where some teachers really struggle. Having been in schools for twenty-five years or so, I saw ICT almost from its beginnings, with BBC Micro, Acorn A3000, A5000, RiscPC etc, and Acorns are still my favourite machine. Then PCs came in, networks, 'whiteboards' etc (Where will it all end!)
The best thing I ever did was during a spell of voluntary help, with a Yr1 Down's boy, who had no language, and couldn't really participate in normal lessons. He loved watching children using the computers, but his motor skills were so poor he couldn't use a keyboard or mouse. I found a web site of disabled activities, that only needed him to press the space-bar as a 'switch', which he could manage. Soon he was launching rockets, jumping chasms, making patterns and many other things, and his little face showed such delight that for the first time HE was in control of the computer!
And please don't think you might not 'be good enough'! Supporting reading doesn't need special skills, just a sympathetic approach to lead the child forward. Talking about books, content etc and inviting the child's ideas is also valuable. Once another Yr1 girl, to whom I must have told some nugget of information that surprised her said, "Sir, do you know EVERYTHING!"