Ideally, it would be GREAT to have seder with grandparents. But consider. I have NEVER had a seder with my grandparents. That is because my two grandmothers died before I was born and my two grandfathers died shortly after I was born. [I had a great grandmother but we were living in different countries so she couldn't join our seder]. My mother and her friends grew up without grandparents because the Nazis killed them all.
So here is a thought: If you have grandparents - be SOOOOO thankful. Focus on the gift you have. Cherish it. Hopefully next year you will celebrate together. THIS YEAR the focus is on keeping them alive....
Being alone for seder: I appreciate and respect the need for people to be with others for the seder. That being said, let me share a personal reminisce. When I go to NY, I often spend Shabbos with someone to whom I really really want to get closer. A person about whom I enjoy learning more about. A fellow that really loves me and I love him and our time together really impacts the relationship in a positive way.
I am referring to none other than myself 馃槉馃槉 . For he's a jolly good fellow....馃幑馃幐馃幏. It is REALLY COOL being alone. Doing introspection. Not being interrupted by technology. Just me myself and I for a rendezvous. Being alone is a challenge but it is also an OPPORTUNITY! To get to know yourself better. To try to think independently. To have peace and quiet.
No - a 3 day yuntif will not be easy for people to spend alone. But with the right attitude it can be VERY rewarding.
Plus, there will be no pressure to keep your seder vorts short. You can talk and talk and talk and nobody will get annoyed. .....