For our kids we got them this a few years back: https://www.thewarehouse.co.nz/p/lego-classic-large-creative-brick-box-v29-10698/R1923582.html
They also have been given numourous sets at various birthdays and christmas etc. They are currently boy 7 and girl 4. They have been playing with Duplo then Lego since their hands could grasp things. Never had a problem with sticking the bricks in their mouths, just keep a close eye on them when first using them. We also have a large mat/bag which we make sure they play on, it opens out to a big circular mat but if you pull the drawstring it pulls up in to a sack for easy carrying and storage.