I’ve got 2 girls and this broke my heart, I’m sorry for your situation but I admire your resolve and the fact you are putting her first.
Everyone in here has had some great ideas so allow me to throw in my 2 cents.
Start and email account for her and you can send emails and pictures to etc but there is also a site called futureme.org which lets you send emails at a specified time (I’ve got one coming to myself in about 5 years saying I hope you have sorted your shit out Dave). You could set up a bunch of emails to send on birthdays, Christmas and other occasions. A bit morbid but if you do get a date when you are likely to go out then you could send one for that date every year.
You sound like a great dad, I hope you can enjoy the time you have left.