Welcome Teachingmykids!
First, I want to say that just by the very nature of you having found BrillKids you must be very aware that children are so much more capable and absorbent than current society gives them credit for...and knowing that, regardless of whether or not you started specific programs as babies, I find it highly unlikely that you didn't teach them things, talk to them, answer endless questions, problem solve with them, sing with them, draw with them, and the myriad other things that involved and loving parents do with their children everyday
All of that is at the very core of what 'Early Learning' works toward.
BrillKids products, YBCR, TweedleWink, language programs, Encyclopedic Knowledge programs, and everything else in the arsenal for EL are simply tools for loving, creative, nurturing parents to utilize toward the goal...and although that specific goal will be different for every child and parent, the ultimate goal of raising happy, educated, independent, strong children afforded every opportunity their parents could manage is universal!
So! It sounds now as though you need some reassurance to ease the anxiety of not beginning an EL program for your children the day after your own 10th birthday!
I can assure you that regardless of when each parent began the EL journey with our children, we ALL have those moments of feeling anxiety, guilt, and pressure to do it all, be perfectly organized, fit in everything we want to!
Somedays I swear I feel like a Supermom, achieving everything on my list, cooking, cleaning, making delicious home cooked meals, running errands, etc...then the other 364 days of the year tend to go a bit pear-shaped
One thing that you might be relieved to realize: I started YBCR with my daughter when she was only 8 weeks old, but I didn't know anything about an EL program, or BrillKids, Doman and the like until last October! Although I now realize that the majority of things I was doing with Alex such as ASL, Montessori activities, our physical program, math, etc., are all involved--I was just trying to recreate the wheel
And here is the thing: whilst I may have started very early teaching her to read, it was several LONG months before I had any meaningful feedback to show for my efforts.( other than the satisfaction of knowing my child was loving it!) Starting a program now with your children? You are going to be able to see huge leaps much faster, and you are going to have SO much fun with it! I personally know of several BK members whose children 'only' started LR less than a year ago, and their young children are already reading and blossoming in so many other ways!
The one thing I would caution is trying to take on too much at the start because you are worried about 'catching them up' or 'making up for lost time.' Remember, you are already much further beyond what most parents are exposing their children to at that age...and your oldest is going to pick it up very, very quickly and you will have a helper to work with your younger kids.
First, you will have to decide what are your immediate goals, and what you might like to add later. The very most important thing will be the reading program, as this will open up so much more of the world. I second the suggestion to try the Marshmallow Math book first, as it is a quick and easy way to empower yourself to make math thinking a priority in your day without the necessity to plan specific lessons or set a lot of time aside..Kitchen Table Math 1 will be next, but it is much more in depth so you might like to ease in a bit. I actually would suggest reading Kitchen Table Math 3 at the same time as the first book, as many of the concepts in the third book can be taught concurrently. (And will greatly help your oldest!)
Have you tried the Little Reader Trial yet?
And one of your biggest resources will be this forum! We are all here to help and encourage you, and look forward to sharing your EL journey.