4 and 6 yr olds like spiderman alot so any toys like that is a good move. You really dont need to spend fifty quid each on that age group as it would be too much.
A remote control car for the 6 yr old would be good but bear in mind that they are close in age and will want each others gifts. try something similar but suitable for their own ages.
or get one big present between the two of them for the garden like a large trampoline. they'd adore that



