The value is not very much, sad to say, UNLESS it’s in good condition cosmetically or functionally. If you have one that looks good and plays well, you have something quite wonderful. I love them.
If you are talking about actual children, I think these harps would be too fragile. I would suggest selling them to a restorer, or investing in restoration and then selling them, recover your money in any case, and get a couple of sturdy newer harps for your lucky, lucky grandkids.
Every time I cast eyes on the harmonic curve of my 1805/1807 single-action Erard, it lifts my heart. I wish I had those thousands of dollars. Then I go and play my elderly but playable old Troubadour, for which I have affection but not the love I have for the Erard..