Battery Backup

[lux1moonprince]

Hi everyone,
I'm thinking of adding a battery backup to my prep stores. Thinking of adding 2 X 220 amp 12v leisure battery's, connected to a mains charger that will topup the battery's once a week.
I only ever intend to use this if the power goes off and I'm happy once I've used it I can't recharge it.
I'm really looking at this to keep the kids occupied for a couple of weeks by allowing iPads etc to be topped up and to run a 12v Tv.
At a later date, I may add some panels to allow power up if the power goes off.
My questions are, should I look for anything specific in a battery? Can I use any charger? If I plan to set this up in a basement, do I need to be aware of any potential issues I.e. Fumes, risk of fire etc.
Thanks