Sorry, but that definition is very limited and insufficient. GO TO TOWN means that given the chance to do something, you do it with uncontrollable fervor - and spending money is the least of it. If I had to definite it in one phrase, it would be сделать что-либо по полной программе - even though that may not be emphatic enough to express this fully.

"Ann threw her husband a surprise party - knowing that he hates surprise parties more than anything in the world. He didn't say anything to her during the party, but after everyone left, he went to town on her." = he yelled at her for three hours -or- beat her to a pulp, depending on what actually happened.

"The kids were so good this year, we decided to do something special. We told them they could paint their playroom any color they like. We bought them 12 cans of paint - all different colors - gave them each a paintbrush and let them go to town." = let them paint the walls any color, any pattern, any words, and do anything they wanted.

"Intent on ruining my wedding, my brother picked up seven homeless people on his way to the reception, brought them into the reception hall, pointed them in the direction of the buffet where they literally went to town." = picked up seven plates and started piling on food as if they hadn't eaten in week AND/OR eating it with reckless abandon.

Развернуться вовсю means сделать все возможное и невозможное, проявиться в полной мере

A: I love the letter - I think you told your father exactly what he needs to hear, but it has a LOT of grammatical errors. I wish you'd let me edit it before you send it. B: Here's a red pen - go to town!

I don’t know what that means, but looking at my examples, you can judge for yourself what’s correct. I don’t agree at all with that dictionary definition.

(Прекрасно) зная, что её муж больше всего на свете ненавидит сюрпризы, Энн устроила для него вечеринку-сюрприз. Во время празника он и слова не промолвил, но как только гости ушли, он дал волю своим чувствам/отвязался по полной.

Дети нас так радовали в этом году, что мы решили сделать для них что-нибудь особенное. Мы разрешили им выкрасить свою игровую, как захотят. Мы купили им 12 банок краски - все разного цвета, дали каждому по кисти и сказали, что они могут развернуться вовсю.

Константин, деньги тут ни при чем.

Спасибо, Татьяна!!

Замыслив испортить мне свадьбу, мой брат, по дороге в ресторан, собрал 8 бомжей, завёл их в (банкетный) зал, показал на столы с едой и разрешил им ни в чём себе не отказывать.

👍🏼😂