Kinda pricey for what it is, but I got one of the goal light buzzers as a gift and it's a lot of fun to have on the wall during games.
This little net is good for 1v1’/2v2 games.
https://www.amazon.com/Franklin-Sports-Hockey-Skills-Goal/dp/B00CE3REKA/
This for use with regular sized net-
https://www.amazon.com/EZGoal-Hockey-Corner-Pocket-Targets/dp/B00E25600I/
15-20 might be stretching it. My daughter turned 2 this winter but I didn't put her in skates yet because the attention span just isn't there - even if she did ask about it a lot. Instead I found a mini hockey set for $10 used on Amazon and she plays that out in the driveway sometimes. We'll get into skating next year.
Found this one which looks the same, but it's $35 + shipping.