My D14 is legally my child, whom I've known and raised as my own for 12 years... yet like you, it remains that I am not her bio father and will never replace that person, no matter how much he is or is not part of her life or is or is not a positive role model in my or other's opinions...
I have seen many step parents counter-mine a child's bio parents and the results appear harmful to all parties. Heck... this happens between bio parents, as well...
We can attempt to protect our children throughout their lives from all evils... but unless we can keep them in a bubble... there's nothing we can do to prevent life from having an affect on them... because what we can control from one vector... can get to them by any of the millions of other vectors...
The best we can do... whether they are our bio, legal, or step children...
Is to love them unconditionally... and at minimum provide for them their basic needs... and be the best mentor and support that we can be... when and if they need. Even a bio child around, for sure beginning around their teen years... are absolutely sure that in many, if not most of their thoughts and beliefs and actions... are right...
Love them unconditionally... and there for your them when life nails them... and all will be good in the world...
Yes, providing financially for them... for their future... is a great idea. Although my only thought on that is that it is money... not love... it is an ACT of love, sure... but it is not a replacement for love...
Also, if there are any public events that you are free to attend, that your kids are attending or participating in... be there for them. Even if they are not aware that you are... because it is a great, parental thing to do...
Once they are adults, your relationship with them is between you and them... that will be up to you to nurture and maintain into the future and theirs to allow or deny...
