[s]Well what i meant by not using Tailmon was more so Tailmon like digimon, but i guess Mikemon works. As long as you're not constantly in Champion form it's fine.[/s] BTW, we wont be using X-Antibody digimon, and here's a list if you need help deciding. http://wikimon.net/Category:Child_Level
Well, the dynamics are just as important as the Plot. As for plot, lets start with a generic ideas to get us started, and branch from there.

An evil force draws the three kids into the Digital world, they meet their partners for the first time, and must work together to fight against this new enemy.
Maybe after the first enemy is defeated, they are sent back to the Real world with their Digimon, but bad things start going on in the Real world too, and they must defeat a threat that entered the Real World with then. When chaos threatens both worlds, the kids must return to the Digital World once more to finish the job.