Gen pdf invoices and mail to client - performance

Hi there,
I would like to know if anybody might have a better solution to help me with what i am doing.
First of all, i will be using a cron which i guess will have to run every 15 to 30 min every beginning of the month.

So when the cron kicks in it will be creating the invoices and invoices items into my DB which then pdf (i have heard of MPDF) will need to be generated (stored ?? not sure yet) then get mailed to the user linked to that invoice. Am i on the right path? or is there something better to do?

Having growth also in mind, i wonder as more clients come on thus more work for the php script to deal with is that above solution will be the final one? thus thinking of making the cron to work on the first 2-3 days of the month and can deal with batches of 10K.

Thanks for all the help,

Regards

Jerome