What a dilemma. I would reinforce your desire for no fuss. Then perhaps compromise. As someone else suggested arrange things to do for the two of you on appropriate dates.
They probably want to celebrate it themselves because you are their mother and parents, so maybe take the family only out for a dinner. Let them pay if cost comes into it!
Insist you do it your way!
What is a reasonable minimum spend for an online grocery delivery??
Being quizzed by chemist's assistant in Boots.
Another Tired Kicking For The Sick And Disabled By Rishi