It's pretty much home parties with decorations and homemade cake until they are tweens (cost $25 or less)...then, if they want, they can invite a few friends for dinner and a movie, ice skating and ice cream, or have a small home party (10 friends)...I try to keep this bill at $150 or less (at least so far), and they get 1/2 the normal birthday present budget from me (since their friends bring presents, so it all evens out)...
I only go "all out" and have to host lots of family and friends for religious ceremonies (every 3-4 years, the way my kids hit them)...and for those, I now do a prix fixe lunch at a restaurant ($20/person + tip for everything), get a bakery sheet cake ($40 or less), and then plan an optional, weather-contingent swim party with bottled water and a homemade fresh fruit tray for all those interested afterwards (thankfully all these ceremonies are once pool season opens)...the pool costs me $2/person, and it lets everyone relax and have "family" time after we do the proper "celebration" (and it gives the out of towners staying in a hotel something to do the rest of the day after the morning ceremony and lunch

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I've done this twice now, and everyone says it's exactly what they want when they come here...so I'll be continuing this one for the next few I have to do...