My oldest kid is still using my old 3070Ti, for 1080p its not a bad card. It gets way more hate then it deserves imo.
Edit:
I am about to drag my 980 Classified out of retirement to use on my youngest's soon to be built first rig..
Should be ok for Roblox
It always surprises me when people describe solid cards like a 3070 as 1080p cards. Do you and your kids only play raytraced games or play at 1080p240?
I have a 3070, and it can run Forza Horizon 4 at 4k120 high settings. I know FH4 isn't a new cutting edge game, but it is still a modern game, a huge open world, with realistic visuals and a PBR workflow etc.
And at the time the 4070 was released at least, TechPowerUp's own benchmark chart had the 3070/3070ti averaging around 4k60 for all the games tested. Very good for a 1080p card, performing 4x better than expected