Definitely assist your children in choosing/purchasing gifts for their mom. That's for sure. As for a gift from you, you might consider getting a 'family gift' ~~~~ something from you that is for everyone in the family. That way you have remembered her with a gift but it's not personal. Another idea - does she have a hobby (reading, gardening, sport...?) You might get her a little something for her hobby - nothing over the top - but something that says "I see you, see that you love [hobby], I support you in it."
Greek, somehow I missed this advice and just now saw it. I do know what her hobby currently is, though I've curbed it quite a bit, and that is her iphone. So I have gotten a few accessories and things to help with that. I did help the girls pick out their gifts. I have one big gift - diamond earrings - had that one planned out for a long time. So make that from everyone in the family, not just me?
M39 W41 Two children WAW bomb dropped 11/7/09 Piecing Aug 10 - Nov 10 No longer piecing...Nov 10 Separation Jan 11 EA ends again Feb 11 Piecing attempt #2, Mar 11