I am old school I got my BB in 1988. ITF all the way. ITF allowed punching to the head as well as other blows delivered with the hands. Protective gear used to be optional and up to the two opponents and it was feet and hand pads that was it. 1 and 3 step sparring was practiced regularly.
Emphasis was on real fighting and real self defense not sports fighting. Point fighting was just a way to see what you had learned and test it in a safe environment. The WTF seems to see the Art as existing for sport first and real fighting and self defense second.
Why are you so concerned about switching? People have multiple BB's in multiple fighting arts so no need to worry. This is not like something earth shattering serious like University Credits transferring from one school to another. Instead of worrying about something like this just let your kids learn and explore the art if you have to move then cross the WTF/ITF bridge when it happens.
I trained in TKD 11yrs., High School Wrestling 1yrs., Boxing 6yrs., Shotokan 1yrs., Judo 4 yrs, and have trained older Army Combatives and Krav Maga. I never felt like learning one art made it hard to learn another. It is kind of like any other thing learning German does not make it hard to learn Russian and learning Chemistry does not make it hard to learn Biology.
I think in today's world finding a good teacher and a good environment are more important than ITF/WTF debate. One and three step sparring, light, medium,full contact sparring and heavy bag work should always be part of training no matter what patch is on the uniform! It comes down to training the core fundamentals!
P.S. Have them learn Sanchin Kata from Shotokan or get John E. Petersons Sprial Bound Isometric Power Revolution book. It will do a lot to improve their speed, strength and power. It will also improve injury prevention. Wish I had that book when I was kid!