Since my kids had b-day parties, from about 4.... in terms of inviting their Preschool friends, I have ALWAYS had their "parties" in the MORNING.
And yes, from about 10:00am.- 12:00pm or 1:00pm.
And we served a little lunch and cake.
AND all the parents of the invited kids, always LOVED the timing of our morning parties. Why? Because, yes, when young, their kids napped in the afternoon. AND when parties are in the morning, then the little kids do not have ALL day long to wait for it.
Morning parties, especially for young kids, are great.
Common sense.
I personally do not like parties in the middle of the day.
I have always planned things like that, in the morning.
And per young kids, parties are typically 2 hours. Then kids are tired, go home and nap.
And young kids are typically better in terms of energy, in the morning.
By afternoon, young kids get tired and/or fussy.
And all of the families/friends we know with 2 or more kids, they ALL are already up in the morning, early, anyway, starting their day already.
I do not know anyone, who sleeps in. Parent or child.
Especially at that age.