Hmm, maybe I'm missing something here but I Created an example with 2 forms. I added a tooltip to each of them. I also added a button to the first form and added this code for it:

Code:
Me.IsMdiContainer = True
Dim frm As New Form2()
frm.MdiParent = Me
frm.Show()
The starup form had its tooltip, and when I hit the buttun the startupform becomes a mdicontainer and opens the second form as a mdi child. The second form also has its tooltip....even if it is a child?!?