Q. If one eats a meal in a public park with his children, when benching what harachaman should one say?
A. On question 2548 regarding someone staying in a Jewish hotel or traveling El Al, whether one should say the blessing for the host after eating and reciting Birchat Hamazon, we wrote: "Mishna Berura (193: 27) rules that one who recites birchas hamazon at a Gentiles house should say; Horachamon – The Merciful should send us many brochos in our ways and our stays forever. He may also say; Horachamon – should bless the baal habais – referring to the provider of the meal.
Chashukei Chemed (Brochos 46a) rules that the same applies to one traveling by plane. He quotes Horav Eliashiv Zt”l, that even one paying for his meal, should bless the provider, since without their help to provide a kosher meal, they would go hungry.
Horav Shlomo Miller’s Shlit’a opinion is that it is proper to say the Horachamon. However, when only the food providers or caterers are Jewish, (as is common in Pesach Hotels), one should mention in the blessing instead of “baal habbais” or the owner of the facility, the term “baal hamazom” or the food provider."
The Rov's opinion is that when eating one's own food at a park or any other public facility, one should only bless his family and children. If there is a separate food provider, he should also be included.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a