I would err on the side of extreme caution. The rules about being a booster, as they have been explained to me, are that if you donate to the school at all- even if it's not directly to the athletic department- you are considered a "booster." I -also used to own family season ticket seating at my undergrad alma mater, and I was told that that alone makes me a "booster."
What NT03 said also seems correct, and yes, it's very difficult to enforce this.
I would think it would be okay to talk to your kids about playing college ball and suggest places to look at, but not directly steer them towards any particular schools, and not press the issue. But check with someone, and be careful.