Tell your kids you love them, all the time. But please, do it spontaneously and mean it. If you find you don't mean it, don't lie. Address your own feelings, learn why you don't mean it, and fix the problem. (Because in the most nonjudgmental-to-those-with-emotional-struggles way possible, if you don't love your kids, THAT'S A PROBLEM.) Don't saddle your kids with an understanding of love that's tinged with guilt or expectations.
My shrink repeats to me, every time I tell her about being insecure about my mothering abilities, "What do kids need the most?" and I answer, "love." But what if our form of love is the problem?
As I've been working through depression, my worldviews and how my childhood formed the adult I am in good ways and bad, I've discovered that there's a difference between what I mean when I say "I love you" and what I hear when others say it to me. I suspect that most other people experience their own versions of the same thing, for the same reason that there's no such thing as a perfect childhood.
When someone else says "I love you" to me, I hear "I have an obligation to you and I'm going to stand by it. Also, I want whatever problem you're having to go away." When I say "I love you" to my husband, I mean, "I desperately need you to love and accept me as I am, but even though every time I've given you the opportunity you've gone above and beyond my needs and helped to heal deep wounds, I'm still afraid to open up because I've lived under certain expectations and related guilt my whole life, so here's my version of what I think good wives say and do." When I say "I love you" to Heidi, I mean "I'm so sorry that my depression makes my obligation to you so overwhelming that sometimes I want to run away, because you are such an important and precious person and you deserve so much better than I can give you, and I never want you to hurt in your life, and if I can do anything to make you happy I will."
These disconnects in the meaning of the word "love" cause me pain in my life and make me feel sometimes like I don't know what love is at all. However, I also know that there are others in the world who hear or mean "I hate or resent you but I can't get away from you" when they hear or say "I love you," and I know that I am lucky for my particular dysfunctional connotative misnomers, since all of mine imply care and concern.
If my therapist is right, though, and I'm sure she is, then surely one of the greatest gifts we can give our kids is a healthy meaning of "I love you." It will follow them into every relationship for the rest of their lives, and even affect their understandings of themselves and their own self-worth. Surely this is worth cultivating. (This is also true with spouses, but that's a different discussion.)
What about you? Do you hear and mean different things for "I love you?" How do you try to ensure that your kids and loved ones are hearing real love in your "I love you?"