Have I committed a forbidden act and missed the opportunity for Hajj, experiencing guilt, because I apologized for not performing Hajj due to my financial inability and my need for money for my young children, even though my colleague went for Hajj?

Whoever does not possess the means for Hajj is not obliged to borrow money for Hajj, and there is no sin upon him for not registering. As for leaving money for children, this is not an excuse for delaying Hajj if the person possesses the means for himself and for those he supports; in such a case, he would be sinful for delaying it, because Hajj is obligatory to be performed immediately according to the majority of scholars.