Honestly, it does get easier as the children get older and their toys get smaller and more expensive. This stage really only does last a few short years - before you know it, your kids will be wanting DS games at £25 a go, and then you really will be thankful for the generous relatives!
In the meantime, encourage rellies to buy toys in the next stage up (particularly for your youngest), then after Xmas,put them away in boxes to get out over the course of the year... so if your three year old is into jigsaw puzzles say, get some people to buy 50 piece ones, other people to buy 100 piece ones and so on. Then put the harder ones away, and by the time you need to get out the harder stuff, the existing toys will be too easy and will need to be put away, thus you will only have half the toys out at any one time, and the other half safely stored away in the attic! I've been doing it for years - keeps the rellies happy so they get to spend, I don't get overrun with toys and as a bonus I do not have to go out and buy lots of harder pressies during the year!
Also, theatre tickets go down well, and next year both your children will be old enough to appreciate them. There are loads of preschool shows out there - show me, show me, Peppa Pig, Noddy, Charlie and Lola, Fifi... you name it!