If you read a bit more around here, then you will see that an EUB is not a real replacement for an UB. Also an UB needs a lot more power than an EBG and Santa not only needs to bring an instrument but also a considerable amount of lessons (at least a year, better two) for that instrument.
If your son really wants to learn upright (and not only want to take it into his hands once a month or a week) a real upright bass (3/4 size) would be the right choice. If he learned it for some years an EUB might be a second instrument for rehearsals or for special cases (loud band, effect sound without acoustic sound) and sometimes also for performances.
A lot of EUBs are made for bass guitarrists, but they lack a lot of the real UB thing, holding is different, neck is often different, which means that major orientation points are missing. Tripod stands nail the player to the instrument at a certain position whereas an UB is usually moved a bit around the endpin.
Also bowing often sounds bad or is difficult because the instruments turns around the axis too much (even with a body support) or doesn't move at all.
Better get a real instrument for an UB beginner! Later you may add a Warwick Triumph Lite or a Stagg with a rosewood fingerboard, that are not too expensive, but (in my opinion) better than a NS Design or an Ergo stick for playing upright.