You might want to Grid the files and then Triangulate the Gridded files and send those over as nice uniform Triangles.
You can also export as DWG 3D faces and import those into Sketchup, that may work better than trying to send the surface across as a TIN
Sketchup does not have a TIN model, and it messes with Triangles that fall on a Plane and turns them into large planar polygons. Sketchup also only has single precision coordinates not Double Precision so it really struggles with large coordinate values - you could try moving everything to 0,0 and then exporting it to Sketchup.Sketchup was developed for architects and all buildings are designed with 0,0 in the mix somewhere - it is extremely good with Building data but it is not at all optimized for big area projects, large coordinates or TIN Surface Models.
It does have some Point Cloud options so you may be able to output the nodes of a surface as a Point Cloud and do something with it in Sketchup.
We don't yet have a way to output a Surface TIN to an IFC object model, I have that on my list of things to look at for BIM modeling purposes.
Let me know if any of these help at all
Alan