Battery strategy for busking amp using 18650s?

Hi all, I am working on a DIY busking amp (thread here), and have settled on the following specs:
18cm x 26cm x 30cm wooden cabinet
B&C 6XT13 speaker
TPA3116 amp (starting with TDA2050 until I get the TPA3116)

I would like to be able to play the violin outside for a crowd of 20 people in a city center for two hours.

Which batteries should I use? I was thinking of using an 18 5Ah drill battery...but...

Then I thought of making my own 14.8V battery pack with a BMS and four 18650 cells inside the amp, and using a power supply (like a laptop power supply) to charge them.

Would four 18650's (with the protective chips) be enough for my use case ?
Is it safe enough to charge them with a charger?

Any advice much appreciated ! Thanks.
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