It's so hard to tell when you're doing the right thing. I usually put the invitation out there when the kids and I are doing something fun the EH might enjoy. He normally says no, but he knows he's welcome every time. I think by asking him he knows we still see him as part of the family. He has actually asked me a couple of times to join him and the kids when he takes them someplace special and that was a really good feeling, not to mention a really fun day. I dont' know if it's right for your sitch, but bf you think it's important for him to know he's welcome then I don't see anything wrong with asking as long as you're prepared for him to say no.
Me 34 H 37 M 12/97 H moved out 03/09 D 05/10 S 17 D 12 S 11