It won't take long for the kids to figure out that you really aren't who you pretended to be, and they will then conclude that you were using them to get in good with their dad.
Just as you enjoy a piece of cake one delicious forkful at a time rather than swallowing it whole; take the time to savor each minute of this phase of your relationship rather than rushing ahead. Here's a common misstep divorced women make when it comes to new relationships: As soon as they've been on two dates with a guy, they want to introduce him to their kids.
Your kids have had enough rough sailing for the time being.
Instead, model for them what it looks like to approach a relationship in a mature manner: slowly and with respect and restraint.
That's a lesson that will serve them well in many ways. Your kids don't get to decide who gets cast as your boyfriend -- that's your decision.
So, you know full well that sometimes things that seem really amazing in the very beginning turn out to be pretty terrible in the end.