You can apply for Fafsa and CSS when they open for filing. Later as you apply to the colleges, you need to go back to your acct at Fafsa and CSS websites and add those Colleges. Each college has stated timeline/last-date for receiving Fafsa/CSS. You need to watch these dates more closely.
If your kids are national merit scholarship semifinalists then there are some colleges offering all the way from full ride to some scholarship for the semifinalists/finalists. However irrespective of financial status or NMF status there are many colleges do offer merit scholarships .
If your financial situation is tight then you may want kids to consider adding instate public schools to the list of colleges they want to apply. In most cases in state public schools are affordable. Hope this helps. Good luck.