We have two kids and the subject comes up in Feb and Sept...It gets tougher to please them as they get to 10 & 11.
Anyway, I can't refer you to any services, but my daughter (soon 11) asked for a home party this time. We have the typical party games, sack races, musical chairs, egg race, then we do an art project or something. We will try napkin technique this time, last time we made ceramic pieces and painted them. Sometimes we used to get a piņata.
We have also had parties at Conneyland, Trampolino, Starbies, McDonalds's, Ravensburger Spielland, bowling & swimming pool, Aquamare and West Side (Bern), and EuropaPark to name a "few". Of course, there's always a cost issue and logistics issue that determine how many best friends they can invite.
Hope that helps.