There is all kinds of data out there on recessions, how long they last, how quickly or slowly things recover, etc.
I'm posting just to point out that you may want to look at your kids' college investments as not one big chunk, but about 8 smaller chunks, one for each semester. Your youngest child's senior year chunks will be invested for about 8 years, but his freshman chunks will only be invested for about 4 years. You may decide to invest the 4 year chunks differently than the 8 year chunks.
With three kids (junior in college, freshman in college, senior in high school), what I do is treat each college chunk separately. I estimate how much it will cost and when it will need to be paid. Personally I just use a simple algorithm of next X years of expenses in bonds and the remainder in stocks. I then know which semesters are invested in which way. I can then look at how long I have between now and when each bill is due, and I can back calculate how much I need in stocks or bonds today to fund each future semester. I then total those current amounts up and get a total stock/bond allocation as well as how much I need in each kids' account.