Torn on gender!

We have a 3 year old son and I am currently 15 weeks pregnant. At first I wanted a gender reveal party but I don’t think it would involve our son much. So, I am torn on how to surprise him...and if I should surprise my husband too. This would mean I would have to make something up as to why I’m “not getting an ultrasound done”...because my husband wants to be there!

Any suggestions, ideas, experience, anything?