Two parties on the same day, WWYD?

I don’t think in this instance it’s rude to leave the first party early. You can just let them know you’d love to attend, however, you already confirmed your attendance at the 2-4 party so you will need to leave early. That’s perfectly reasonable.

Leave the first one half hour early and arrive at the second one half hour late. Explain to both that you’ve got two parties and this is the fairest way to attend both

How old is your child? Would they have the stamina to attend both parties or would they be burnt out and tantrum-y by the time you get to the second party?

I’ve done that before, left one party early to go to another midway accidentally double booked myself it wasn’t a kids party though it was 2 on NYE lol but yes it’s doable if you leave one a lil early. I did have to tell them I had another event on and they were understanding as in my social circle it’s very common for someone to say “oh I gotta leave a lil early I have another event/party on” I wasn’t the first to say that lol.

Personally would just go to the first party. If I hadn’t seen the others in a year I’d just make my apologies that you already have a party and ask if you can arrange something another day together.

That's fine and getting 10 minutes late isn't a big deal as hosts are usually running late i usually am lol.

I’d go to both

I think with the timings I’d just go with the first one you’ve accepted. If it was ten minutes away it would be slightly different.